Demon Gas Cap HELP!

Hi all,
I have a '71 Demon, built in October 1970 in LA. It has that extra vent tube in the trunk. Fender tag has N95 on it which I believe says that is a CA emissions car. Anyway, my gas cap does not fit. It is loose. It seems the prongs need to be closer to the gasket. What type of gas cap will fit my car? Any help is greatly appreciated.