Hardcore,
There are a brazilian possibilities, but LEDs are probably the way to go. They use a lot less power, are lightweight, and the "bulbs" last almost forever. I started with an old Justrite electric lamp that used a belt mounted battery holder for 4 D-cells, tried a 6-volt gel cell so I could recharge it, bought a Petzl Mega with a a halogen bulb and a back-of-the helmet mounted battrey pack that holds 3 C-cells or 3 AA-cells, and a few other home brew designs.
I just got a Petzl Myo XP LED lamp for $50 on sale from REI. It's about as bright as my old halogen lamp, and a whole lot lighter. It's not the brightest available, but it's a nice piece of gear.
If you like to tinker, there are a number of places to get bulbs, LEDs and batteries. The reflector is probably the most important and most difficult thing to scrounge. You need to be able to change the focus or use some sort of diffuser to broaden the beam occasionally and if you use LEDs, you'll need some bit of circuitry to drive them. Some links:
LED stuff
http://www.photonfanatic.com/
Bob and Bob, lots of parts
http://www.4bobandbob.com/
It just depends how much you want to fool around with the stuff. Have fun.