The gas cap on the 1100 is expensive. Most gas tank gaskets are somewhat universal. Might try taking your gas cap in to your local auto parts store and see is they have a similar size cap the fits a car. You would have to buy the whole gas cap to get the gasket but $10 beats $100 for new Yamaha gas cap. Years ago I cut a gas tank gasket for a dirt bike out of an old inner tube. It actually worked pretty good keeping gas from slashing on me. Plus it was free.