If you feel that it is visibility that is causing you to be buzzed consider wearing a reflective safety vest and adding additional reflectors or reflective tape to your bike. Reflectors are more effective than most blinkies for providing visibility to cars from behind because you are using thier lights. Heres the vest I use
http://alertshirt.com/clas2safves.html
Or you could hook up one of those semi trailer lights like mentioned in another thread.
Craig