Find a bike store that sells used stuff and look for the older Union bottle dynamo sets, I pick these up all the time for less than $10 complete with lamps, they usually work just fine; just spin the bottle first to make sure the bearings are good, you really can't test the output unless you mount it up on a bike first. For replacement bulbs for older Union lamps that use bulbs w/ screw-in bases, I buy from Reflectalight:

http://www.reflectalite.com/halogenpage.html

They've got halogen or regular screw-in bulbs for the old Union lamps (halogens: GH93 or GH106, depending on whether you're also using a dynamo-powered taillight; GV605 is their standard bulb). Reflectalite also sells dynamo regulators so you won't burn bulbs out going fast downhill:

http://www.reflectalite.com/regulater.html

Reflectalight's service and delivery times are excellent.