Terra-Lux makes LED plug-in replacements for the Maglite series of flash lights (and probably others).
The ultra low current high efficiency LED upgrade is advertised to extend battery life significantly. They are available in white, green, red and ultraviolet (UV).
Some models of the white unit are advertised to be brighter than the old incandescent bulbs. (Be warned that the “beam†from the LED upgrade is different from a conventional lamp; depends on what you are wanting) Also, note that the LEDs are driven by integrated circuits expecting to see pure DC battery (typically 3V), so anyone trying to use these in an “experimental aircraft†application would need to be concerned with filtering, spike suppression, polarity reversals and a regulated source of DC to match the design voltage. (home brew, Radio Shack, etc.)
I plan to upgrade several min-mags to red (we’re talking hi-efficiency spectrally pure red –none of that wasteful cheap red plastic filtering) for occasional night cockpit use. Since they are battery powered and Velcro attached, I avoid Imperial entanglements.
I tried the UV upgrade for a mini-mag for fluorescent dye crack inspection during shop class last semester. It was no match for the 200 watt shop UV inspection lamp. (It was advertised to show air conditioner leak dye) perhaps the next generation of LED will be shorter wavelength and higher intensity. It wasn’t a total waste though, as CSI fans know, I can easily find every spot our tom cat has ever marked on our carpets…