Any hot tips on replacing gas tank filler tube grommet?

Right, early A's had smaller diameter filler tubes, it ain't gonna work tryin' to use the later one & You're just going to have to wait 'cause I don't know of any way to install
the filler after the tank's in.
No doubt! As soon as I received my new grommet quickly found out I had to drop the tank in order to finagle the filler tube out. Once apart I found my new grommet was a tad too big and my old one has a more flared inner seal.
Any idea where I can find a match?