I made this out of a piece of scrap cedar 2X4 that I had lying around.
Step 1: Need Scrap Cedar?
Look in your local yellow pages for fencing companies or other places that make things out of wood. Give them a call. Ask if you can have some scraps. Make sure you talk to someone who has the authority to give you permission to dig through their scraps - remember their name. If anyone bugs you later, you can say "Bob Smith told me it was OK, give him a call."
Chances are the scraps will be in a dumpster "out back". Go there and pick out what you want. Mostly it will be small scraps (duh!) but occasionally you might find a larger piece which isn't good for making their wooden thing, but might be perfect for what you need. I've found 3 foot long 2X4's - good for building 'stuff' at home, but not much use for building a fence. They generate so much scrap it isn't worth it to them to save those pieces for re-use because they'll be making more of those scraps tomorrow. Always plenty of scraps around for when they might need one. It's a shame really, some tree labored hard, surviving a multitude of hot summers and cold winters, to produce that beautiful wood. As with at any lumber yard, watch out for protruding splinters, nails, screws, staples, etc. Oh, and by the way, this is a good way to get free firewood too.
Another option might be the local lumber yard. I know Home Depot typically has a 'scratch and dent' bin located somewhere near the back of their store. They use it to get rid of pieces of wood which aren't up to snuff. Say a badly warped 2X4, half of a broken sheet of plywood/drywall, some roofing shingles which broke out of their bundle, etc. It will be marked as being special and hopefully clearly labeled so when you get to the cash register they'll know what to charge you. If it's not, save yourself a hassle and either pass on it or find someone to label it before you take it to the register. I've made a habit of passing by this bin whenever I'm in the store, you never know what might turn up back there.
Step 2: Plan
A: Either a disaster, an incomplete project, or if you're lucky something that can be re-worked/salvaged.
I figured out about what size the knob would need to be. I guesstimated an outside diameter of about 1 inch larger than the handle. I measured how thick the stop collar was (this would need clearance to rotate in the knob). I guesstimated about how far onto the handle I'd like the knob to fit.
Two of those factored into my choice to use a piece of 2X4. I needed something thick enough to house the stop collar and allow the depth for the handle.
Step 3: Drills Some Holes
I used a Forstner bit for this. If you don't know what that is, it's kinda like a spade bit and a hole saw combined. They drill nice round flat bottomed holes. They have a brad point in the center to guide it. That's why I drilled the big hole first. Drill the small hole first and you don't have any wood to rest that point in when drilling the big hole.
I drilled the big hole to a depth equal to how far I wanted the knob to stick onto the handle - about 3/4 inch. Then I drilled the small hole to a depth that would allow clearance for the stop collar - about 1/2 inch deeper than the big hole.
Step 4: Make It Round
Miter saw to the rescue! I cut it into a square on lines tangent to the circle I drew earlier. Then I cut the corners off of the square on lines tangent to the circle too. Then I cut the corners off the octagon, again on tangent lines. That leaves you with a hexadecagon - a polygon with 16 sides. At this point, it's pretty much pointless to attempt to continue to cut off corners. I knocked the remaining corners off with a rasp and then sand paper.
You can probably see in the picture that I didn't get it perfectly round. I'm OK with that, this is a knob/handle, not a wheel.
Step 5: Round the Corners and Install
Press it onto the handle of the hand drill and get to drilling. I like it. I can brace it against my chest or stomach while I drill - it's much easier than using the 'old' handle. Now I'm thinking I might chop that old handle down a bit so all I have is a couple of inches sticking out of the knob.