I am looking on ebay for a good seat new or in very good used condition. The seat that came with my bike hurts me. It is a San Marco that came with my 1986 Schwinn Prelude. Is there a formula for seat width? The middle of my seat bones is about 130 millimeters apart. I seem to be drawn to the the Selle Italia seats. They look great. What width should I be looking for? Any recommendations on a nice seat for around $ 40 or $50 new or used?