I bought a NEBO #5550 HIGHBEAM Rechargeable Light that uses a car cigarette lighter outlet to recharge for only $10.
I found it really handy to carry around, and thought it would make a great bike head light if I could figure out how to make it stay on the handles bars, but still be able to take it with me, to keep it from getting stolen.

Even militant car hating cyclists can use it if they buy a 120AC to Cigarette lighter adapter like this:
http://www.newertech.com/products/120_12Vadpt.php

If your hardware store doesn't have the #5550 HIGHBEAM Rechargeable Light
you can get it here:
http://www.nebotools.com/prod_details.php?id=91&cid=&subid=&subsubcid=

Step 1: Stuff You Need

See notes for descriptions

Step 2: Get a Tube

I found this pvc toilet overflow pipe at a hardware stor for a couple of bucks, it's long enough you could make several light housings. The NEBO light fits into the tube, except for the bezel that rotates to turn the light on/off. This tube has a inside diameter of 7/8"

Step 3: Cut the Tube

I cut min as short as I could, but depending on how you want to cap the end you may want to make it longer. I used a pipe cutter, but a hack saw would work too.

Step 4: Dress It Up

I had a piece of sign vinyl laying around, but you could paint it or just leave it white.
reflective tape would be cool too.

Step 5: Cut Two Slots

I used a dremel tool, but a hack saw would probably be better. This is where the strap will thread through. I used an x-acto knife to clean it up.

Step 6:

I had this velcro strip laying around, that has the hooks on one side and loop on the other.
I think you can get these at a bike shop or REI, or just use a zip tie, or maybe even a nylon strap with a D-ring.

Step 7: Drill Small Hole

I drilled this hole in the body of the housing to help hold the Sugru in place in the next step.

Step 8: Sugru!

I put some Sugru under the loop of the strap inside the tube. This is where you will want to see how the light fits. My strap was thick enough to hold the light in place with just small glob of Sugru. I also used Sugru on the outside to make a nice rubbery cushion that conforms to the shape of the handlebar. The Sugru on the inside conetcs with the Sugru on the outside to form one solid piece when it cures.

Step 9: Texture

I used the hook part of the velcro to add some texture to the Sugru. This should help it grab the handlebar better.

Step 10: Put a Plug in It

I glued a bottle cap on the end. You could leave it open, but the rain might get in.

Step 11: Go for a Night Ride

You can add more Sugru to the inside of the tube to shim it enough to get a snug hold on the light. It should slide in and out of the housing, but still be snug enough to turn the bezel on the front, that turns the light on/off.