After dealing with it long enough, I decided to see what I could come up with. I wanted something cheap, and easy to disassemble so it wouldn't affect the portability of the stroller. I came up with two different handle designs. It cost less than a dollar more to make both, so it's worthwhile to be able to test both and see which suits you more.
Step 1: Materials and Tools
These are the materials I used, however, different stroller models will likely have different needs. Use this list to get a general idea of what you will need. I used 3/4 PVC because that's what fit the handles of my stroller. I stuck with 3/4 throughout as I figured it'd make a stiffer handle. It is easy to switch from 3/4 to 1/2, or 1/2 to 3/4 if needed. The best way to determine what suits you best is to wheel your stroller into a hardware store and start testing different fittings.
Velcro Ties - $4.99
PVC Cement - $3.38
1 - 3/4 PVC 5' - $1.49
1 - 3/4 Self Seal foam pipe insulation - $1.50
1 - 3/4 PVC Tee - $0.33
1 - 3/4 PVC Cap - $0.39
2 - 3/4 PVC Snap Tee - $1.32 - Basically a tee with the bottom cut off to allow snapping onto a piece of pipe.
2 - 3/4 PVC Threaded/Slip Elbow - $0.91
Most folks probably have these on hand, or can borrow them for an afternoon.
Hacksaw - for cutting the PVC to length
Utility Knife - for cutting insulation
Sharpie - for marking stuff
Not pictured - Tape Measure - for measuring stuff
Step 2: Handle Base
Take your snap tees and slip them onto the stroller handles. They should fit snugly, but will doubtless move around a god bit. That's ok. They are made to slip on and off, so some play is to be expected. Position them anywhere convenient for now, you can always re-position them as needed later.
Take a couple of the Velcro ties and wrap one around each end of the snap tee. Make these as tight as you can. Feel free to ignore the little loop you'll find in one end of the ties. It will tear out as soon as any tension is applied. Just wrap them as tight as you can. These will hold the snap tees in place well enough to allow you to tip the stroller back to get over curbs and such.
Lastly, screw in the elbows. Don't worry about screwing them down as tightly as you can. Just give them a few turns, until it starts getting harder to turn. Then look at where they are pointing. You need the open ends of the elbows to be pointing towards each other. If you can continue tightening the elbows so they are facing the right way, great. If you have to loosen them a bit to get them correctly positioned, that's ok too.
That's it! Handle base = complete.
Step 3: First Handle
Lay your pipe across the elbows of the base. Make sure the elbows are pointing directly at each other, using the pipe as a guide. When you're set, mark the pipe for cutting. You want to ensure there is enough pipe to connect the elbows, remembering that some of the pipe needs to sit inside the elbows. At least a half inch on either side should be sufficient. I wouldn't bother with a tape measure. Just eye-balling it is fine for this project, and faster to boot. Now take your hacksaw to the mark you made and cut. Remove the burrs and insert the pipe into the elbows.
One handle done.
Of course, this handle wouldn't be very comfy to use, so we'll add that pipe insulation as a comfort grip.
Measure the insulation the same way you measured the pipe. Lay it on the handle you just made, till one end rests against the edge of an elbow. Make a cut at the edge of the other elbow. That should leave you a piece of insulation that fits just right. Slide the insulation over the handle and peel off the cellophane. Press the side of the insulation together to form a solid tube.
I've found that leaving the insulation as is doesn't work so great. The heat of a parked car, banging around in a bag, or even handling can cause the seam to separate. You can keep pressing the seam together, but the hold just gets weaker and weaker. One solution is to use some of the Velcro ties to secure the insulation. Just wrap a tie close to either end. The ties don't have to be super tight, just enough to keep the seam from puling apart. Works well so far. Just remember to keep the softer side of the Velcro facing out, so it won't bother you if you hold the handle there.
Step 4: Second Handle
This handle starts out the same way as the first. Measure and cut a length of pipe to fit between the elbows of the base. I just used the first handle as a template. After ensuring the new handle fits correctly, mark the center of the pipe, length wise. Use the tape measure here, and try to get as close to the center as you can. This will make steering easier. Now, hold a tee up to the center mark. Make two marks on the pipe, one for each side of the tee. Remember, again, to account for the amount that will reside inside the tee. Saw the pipe at the marks for the tee. The end result should be about a one inch gap between the two pieces of pipe when inserted into the elbows.
Install the tee between the two pieces of pipe you just created. The handle should be sturdy once again, but now features a socket for another piece of pipe. Insert the remaining pipe you have into the tee on the handle. How long to make this bit is personal preference, as everyone's hands are different sizes. Grip the pipe with one hand. Give yourself some extra space for adjusting your grip and comfort, and mark the pipe. Cut at your mark and re-insert the pipe. Add the cap on the end to give it a more finished look.
This is the only piece you'll need to glue on. I've had the extension handle come out on me several times, usually while walking downhill. As this isn't actual plumbing work, you can skip the cleaning step and head straight into cementing. Apply a good amount of glue over the last inch or so of the end that sits in the tee. Insert the extension handle into the tee while twisting to ensure a good bond. Wipe off any access. The extension is now secure.
If you disassembled the handle to glue on the extension, reassemble it now. Cut and apply the pipe insulation in the same manner as the first handle.
Second handle is done! Yay!
Step 5: Usage and Closing Thoughts
Using the first handle is pretty straight forward. Grasp handle, walk. Easy stuff.
The second handle is really just as easy. With the extension pointing back horizontally, the stroller operates in Mail Carrier Mode. Steering is very easy, and good distance is maintained between walker and stroller. Other positions are possible, as the extension can rotate a full 360° around the main handle. With the extension pointing down the handle operates just as the first handle.
Removing the handles are also easy. The tension of the fittings keeps things in place pretty well, but some twisting will loosen things up nicely. A couple twists of the handle will allow you to pop one side out of the base. The other side can then be easily removed. The Velcro straps on the base still allow the snap tees to rotate on the stroller handle. This also facilitates removal of the handles. Only the extension handle is glued on, so if some TSA agent is concerned, the entire handle can be disassembled in no time.
The small increase in height the first handle gives is just right for my wife. I find it allows me to position myself at the back of the stroller in such a way that my feet don't interfere with the wheels, and vice versa. It would be very easy to extend the first handle out for taller folks, though. Simply swap out the thread/slip elbows for straight thread/slip adapters, and standard slip elbows. The length of pipe needed to connect the adapters and elbows can be made to any length, accommodating even the tallest people.
The extended "T" handle can also be adapted further. Instead of a cap on the end, another tee can be used. With some pipe extending out both sides for the new tee an "I" handle of sorts can be created.
Many designs can be made from these simple handles.