71 Dodge Demon Fuel Cap
I assume the '71 Demon has the same 1 year only gas cap as the '71 Dart.
I gave up looking for the elusive '71 cap for my '71 Dart GT and went with a '69 Charger fliptop cap.
I've also purchased a filler tube and (painted) cap from a '73 Dart Swinger if I ever get bored with the fliptop.