Any source on replacement gasket for 71 gas cap?

I would be shocked if anyone would repop the gasket. That's a pretty obscure part. AMD has replacement caps. 1971 Dodge Demon Fuel System - Gas Caps Fuel System - Gas Caps
They never show the back of the cap They are all 67-70 or 72-76 caps. Have not seen any fit a 71.

Just buy a cap anywhere and steal the rubber.