Gas cap grommet 1968 Dodge Dart

If you can get in touch with the cap manufacturer, they may have the seal you are looking for. What you have looks like a Stant locking gas cap.
Great idea, thanks a lot!
Maybe you could steal one off this cheap cap or use it until you find the right one.
1968 DODGE DART 5.6L 340cid V8 Fuel Tank Cap | RockAuto
Again: great idea! Now that I know that it is a Stant locking cap I will check. Thanks!
Might be but I will try to get a new grommet first.