I recently bought a 2 watt Blaze light from Planet bike for $40 from eBay. I didn't like the beam pattern too much (too narrow, it uses something similar to a TIR instead of a reflector), and the tint (slightly purple).
It turns out the head cover is a snap in (snaps on the left and right sides of the light), and when taken part, there's easy access to the LED. The CREE XR-E is mounted to a rounded rectangular 16mm x 22mm PCB, which is soldered only by two wires. This PCB is secured to the aluminum body by two small screws.
All in all, it looks like it'll be easily mod-able with another drop in PCB (20mm star should work with a bit of thermal epoxy, drilling, or other way to mount it.
If anyone's interested or has ideas, let me know! I considered dropping in a XP-G Neutral on 20mm star, but decided it wasn't enough of an improvement to spend the time and money on.
Pictures at web album: http://img16.imageshack.us/g/img0214xp.jpg/
And here's one of the six pictures: