I've made a few. For example, ripped the guts out of a US$3, 7 LED, 3xAAA light, put a K2 or Cree with optics or reflector, and a regulator (home made or more recently from DX or KD) with a two position switch, mounted it on the front of a helmet, run wires to the back and mounted 4xAA cells there. And then (sequentially) taken them caving, of course.