My friend had an Insight M3 or something similar on his.
DS Tactical has the Surefire X300 for about 270-280 bucks, you WILL need a small section of Picatinny rail to mount it on though.
I think there are some similar styles of light (kind used to mount on a handgun) that are less expensive though, the Streamlight TLR-1 I think is pretty good for a bit less.