Introduction: My newly designed light uses a 50mm lamp, aluminium tubing, nylon end caps, and runs much cooler (partially due to the IRC lamp). Total cost for building one of these lights with a battery and charger is less than $120. Run time depends on Ah of battery, 7Ah = ~2h20m. Click on any of the images for higher res versions.

Shopping List:
· 1x 12V Sealed Lead Acid Battery + Charger · 1x 50mm 24o 12V IRC Halogen Dichroic Lamp · 1x Lamp holder for above · 2m 10A rated cable (Tru-rip or similar) · 1x 10A 12V SPST (or SPDT) switch · Assorted crimp lugs, joiners (or use solder)	· 50mm Round Aluminum Tube (thinnest wall, only sold by the metre so may pay to group buy this purchase.) · 1x #8735 51mm Nylon End Cap · 1x #4761 50mm Nylon Plug
These are the suppliers I used for all the parts listed above:
Rexel Christchurch (121 Tuam St) · Lamps, Holders, Battery, Charger & Cable. Dick Smith Electronics (Cnr Colombo & St Asaph St's) · Switch & Crimping gear. Para Rubber (94-96 Manchester St) · Nylon End Caps. Mico Metals (12-26 Balfour Terrace) · Aluminium Tube.
· These parts are quite common so it shouldn't be too hard to come across them in other cities / countries.

Step #1: Laid out in the picture are the majority of the parts you need. Start out by cutting yourself a 100mm length of your aluminium tube with a hacksaw. For heat dissipation I drilled four 6mm holes in the tube, two in each side.

Step #2: Take your two end caps, the one on the left is the rear end cap and the one on the right is for the front. You need to make a 45mm hole in the front end cap, I used a hole saw on a battery drill for this, but you could use a medium sized drill bit and make a number of holes, clean it up with a craft knife and file. Depending on your switch and cable you may need to make different sized holes in the rear end cap, mine required a 6mm hole for the cable and a 20mm hole for the switch, I used a 20mm spade bit for the switch and a 6mm drill bit for the cable.

Step #3: To make the front end cap easier to get on, I cut it down to about 20mm as you can see from the before and after pictures.

Step #4: I've used crimp lugs to wire up the light, you can solder if you like. Tie a knot in the cable going into the light so it won't be pulled out, run one power cable to the switch, the other to the lamp holder, then run the other wire from the lamp holder to the switch. Leave enough length so when inserting the lamp you will be able to pull the holder out the front of the tube. Check that the switch powers on the light as expected before continuing.

Step #5: From this view you can see how your lights should look when assembled. Firstly put the rear end cap in, this takes a fair amount of force, push it and the tube against a bench or table top, once it's in it ain't going anywhere!. Pull the lamp holder out far enough to put the lamp in then rest the lamp against the edge of the tube, now carefully put the front end cap on, work it slowly from left to right up against the edge of a bench, do this until the lamp is no longer able to rattle about.

Finished Product: Hopefully by now your light should look similar to this, I simply zip tie mine to the top of my helmet using the vents, or you could use a velcro strap or similar. I have put a connector on the power lead to the lights to make life easier, they're commonly used on Tamiya Radio Control car batteries and available at most hobby or electronics stores.