search google for glow sticks or a dive or marine shop would have them, Craig on teamcyberspeed used them during the Mugg Drift and they worked great. I used to use a battery operated red/green and white flash light which always was dead when you needed it.
Also if you go for just the flashlight idea (legal but not safe) make sure it's always on not just when you see a boat, this I learned the hard way from the coast guard.