Just go to a car parts store and get two halogen driving lights (they usually come as a pair - sell one to a friend!) They'll probably be 50W, though sometimes you can find 35W. If it's 35W you can probably keep it like that, otherwise you'll have to go out and get a 12V MR16 bulb in the 20W range. Combine this with a nice 12V NiMH or Li-Ion battery pack and waterproof switch from batteryspace.com, and you're all set! The whole rig will easily cost less than $200, will look good, perform well, and it'll be totally waterproof.