I just picked up an 8 inch 'electric light stick' from Walgreens for $1.99. See: http://www.walgreens.com/store/produ...id=prod1679766 It has 5 LED's along the shaft of it and a button that allows you to cycle through different flash modes. I have it mounted horozontally on the back of my rack and I set it to 'knightrider' scanning back and forward. It is very bright and it uses red, blue, and green LEDs so I believe it is more eye catching than a simple 'red' blinkie. I doubt it is waterproof but I don't ride in the rain so that's not a problem for me. It could be covered in a piece of saran wrap or something for anyone who does need water resistance.

I'm sure the batteries won't last forever but...

Many of theses types of lights use LR44 'button cell' batteries. If the batteries in my blinkie die, instead of going and buying 3 new LR44 batteries for $2.99 a piece, I go to the Dollar Tree and but a $1 'LED clip light' or something similar and pop the 3 LR44 batteries out of it and into my blinkie. I can desolder the led and switch from the clip light and save them for future projects, and i just got 3 new batteries for less than what one would cost.