Re: Harbor Freight self contained engine electrical output?
I've had good enough luck with a used 6 volt bottle type generator that rubs against the tire, like what Dan was describing. I make my own lights using the guts from cheap little led flashlights meant to run on 4.5 volts. The LED lights have a lot more tolerance for varied voltage than incandescent bulbs which will burn out at higher speed. The cheapest route is LED lights and a 6 volt used generator from ebay or a scrounged bike. I have yet to do it, but adding in a capacitor to briefly store some voltage will allow you to come to a stop and still have your lights lit up for a bit, hopefully long enough for the traffic light to change and be off again generating voltage. I think that would be just a bout the cheapest, reliable setup one could do. Not necessarily the best, but good and highly affordable. Some kind of lights is way better than no lights.
Someday when I grow up I will probably lose interest in toys with wheels, but until then...