I didn't think to build my wheel with a dynamo, so when I decided I wanted classic lighting for my Raleigh Sports, the options were pretty limited. I bought this old Ellite lamp that clips to the light bracket.
2 D batteries and a 2.7v flashlight bulb. It actually put out pretty good light - more be seen than see of course, but it did actually light up the road a bit. However, battery life was subpar.
I was thinking of getting all fancy and wiring an LED cluster into it, but then I found a site selling LED bulbs to retrofit old flashlights (http://www.superbrightleds.com/cgi-b...t%2Fbulbs.html)
I ordered one ($10+ shipping - ouch) and now my old light is blindingly bright. Sure, I'll miss that warm orange incandescant glow, but batteries are expensive and thise bulb should keep that set of D bateries going a long long time.
I assume these bulbs would work for Dynamo lighhting too.