Had an idea this afternoon while scheming up homemade headlights. Haven't tried it yet, just an idea.
Anyway, there at the auto parts place, they sell trailer lights, self-contained little lights for tail lights. Then over in the Bulb department, they sell a replacement bulb for taillights that has a dozen or so LED's instead of a filament bulb. I don't know what the power draw is, but that might be one way to get a fairly bright taillight withough much current. (The LED's are wide-angle, so you wouldn't want to try them for a headlight.)