The surefire would work fine. One caveat (although I'm not a surefire person): IIRC Surefires tend to all run off of the very expensive non-rechargeable Lithium cells. For both your wallet and the environment's sake, it is probably wiser to use a light that runs off of rechargeable batteries. There is one maker of voltage-suppressed (3.6->3.0 V) Li-ion rechargeables for the Surefire, but that's an uncommmon item that you'd have to order online.

If you get a different light, be sure to get a smart battery charger since overcharging batteries kills them. Charging speed isn't all that crucial, and reports have it that the super-rapid chargers (ones that charge a fully-discharged battery in 15 min) reduce battery life.

In terms of mounting, do a search on EMT hangers or something like that around here to find clamps to mount to the bike. I have a vague memory about how bicyclelighting.com had a link to some clamp manufacturer too.