If I recall correctly, Wolf Eyes makes some tactical-style multimode (2 mode?) modules like that.
Xlanc, you don't really need to upgrade the 6P, it's pretty impressive out of the box. That said, the Lumens Factory bulbs are some of the most-loved incandescent lamp upgrades here, with voltages to suit rechargeables as well as primary cells.
For LEDs, I'm pretty fond of my Malkoff - throws like a pocket spotlight, excellent mid-range light with enough output to make an average household room comfortably bright to walk in with a ceiling bounce. I also considered a few from DealExtreme, but eventually decided against it - first when I decided I wanted a 3p (lol, expensive) and then when I realized that I could afford the M60. Lots of people like DX part #6090; it's very well-documented, and supports a very wide range of operating voltages - 3v to 18v, or 1 to 6 123a cells.
Any way you slice it, that little gem's gonna shine.