I'm not sure if Peak are still making semi-custom lights? At one point you could specify the color and number of 5mm LEDs for the flashlight head, as well as the type of battery tube body (1xAAA, 2xAAA, AA, CR123, etc), and they would build it. The circuitry was designed to work with either primaries or a wide variety of rechargeable chemistries, such as NiMH or Li-Ion.