Cdmgear makes some nice clamps. I just got the Mod C. If I had to stay around $100 dollars, I would get a Streamlight PolyTac LED light to go with it. You can get the light for $45 dollars on Ebay and the clamp runs $55 dollars plus shipping.
I would rather have a G2, but the light will run you $111 dollars if you add the click on tailcap option and I would rather have one that way, than one you have to turn the tailcap.The PolyTac has a click on switch.
I am waiting for opticsplanet to get the new 120 lumen Surefire 6P Defense in stock. That's what I am going to mount in mine, $112 dollars.