I agree with cyccomute above. The P7 flashlights and handlebar mounts are the way to go. You would have to pay $200+ to get anything as bright that was made specifically for a bicycle. Follow Cyccommute's link to the thread.
When my old bike light that my wife got me as a gift dies, I'm going to get a P7 myself. I've personally seen them in action, and they are BRIGHT and rugged, and much less expensive than something like a Dinnote or NiteRider light with similar brightness.