Took me a while to figure out an approach. First make a clear plastic bike helmet. Coat it with a thin layer of waterproof phosphors. Liberally attach UV emitting LEDs inside the helmet pointing outward. (no need to sunburn your scalp) Wait for night and power up the LEDs. Presto, glowing helmet.

OR: Cover the helmet with Tritium powered night-lights.

OR: Use black-light paint on the helmet and have one of those stealthed Black Helicopters follow you with a UV spotlight.

OR: Have a Neon sign artist build a neon tube cover for your helmet and plub into a power supply in a pannier.

OR: In the old days you could use the radium paint once used on watch dials.