Batteries.com has them, including rechargable ones:
http://www.batteries.com/index.asp?s...atchpartialmax
I have a Surefire 6P light. With the original bulb it would eat these batteries very quicly.
Some time ago I replaced the lamp with an LED. Battery life is anywhere from two to four times as long. And, unlike the regular bulb, the LED slowly dims over time, but even at lower power leaves a decent amount of usable light.
Once the regular bulb hits the wall, though, it's lights out.