A couple years ago, when Nichia LEDs were first coming out, I knobbed(Kluged) an LED conversion for a 3 D cell mag lite using 7 LEDs and some perf board, a machine screw and a couple nuts, some serious soldering, and some wire. I sold the thing to a guy for $50 and never made another. The writing was on the wall, and I wasn't in a production mode at the time.

It did work pretty good though. Reflectors don't mean much, the LED light is already focused at a pre-determined angle, with very little backscatter for the reflector, but what the heck, people like to crank the end I guess.