You can get small Xenon strobe lights in several colors. Mine works on anything from 6 to 15 volts. When I go night kayaking in San Francisco Bay I take mine off of the bike, wire in a 9-volt battery, and paddle off. For serious power get a bigger battery and a PSE amber warning strobe light. Light goes in all directions, not just to the rear. Even my little Radio Shack strobe is strong enough to be a sure cure for keeping people from drafting me.