mount an ergo tri rail foreend, with a rail type flashlight, whether it be a surefire x300, stramlight m3 or tlr-1, or tlr-2 if you've got the bigger bucks, and your done.
or if you have a 1" diameter handheld light, you can get a flashlight holder that has a rail attachment, i've seen some at wolverine, i believe they were by command arms, and they were 20-40 bucks i believe.
with mine i also added a stubby vertical grip so my hand doesn't hit the light or slide in front of the muzzle.