Gas Cap that doesn't leak?

[67Fleetsidedream]

I have a gas cap that leaks like crazy every time I take a right turn. It is only 4 months old and it not one of those crappy Autozone ones. It is one that has the rubber compression gasket. Does anyone know of a place that makes a gas cap that does not leak or allow fuel to escape the gas tank inlet when turning. I can not predict my gas mileage due to the half a gallon of gas I loose every time I take a right turn. It would also be nice if were a locking type cap also. Can anyone help me?

Thanks
Ben