Oconeedan,
i realize you said you didn't want to spend the money, but these are a really great product Yamaha Motorcycle Taillight- Custom Dynamics - Yamaha LED Brake Light
I have used them in the last three bikes and they really make you visible. I haven't tried them personally, but the LED shaped bulbs are reportedly a waste of money.
i also use the Custom Dynamics modulator to flash my brake light and since I have a Venture, I have a light bar under my trunk sold by one of our members.