fuel filler grommet

well we just had to replace the fuel tank on my sons 74 Duster, had a hole rusted through on the top right where the trunk drain plug was, ( which was leaking ), kind of a shame as the tank was damn near perfect other than that, Arizona car, no rust any where else, not even any sludge in the tank, anyway, got it all back together and it leaks from the fuel filler grommet where the neck goes in the tank, the tank was a Scepter I believe?, made in Canada, nice tank but surprisingly no new grommet came with it, only the one for the sender, we got it at Napa and they said they couldn't supply a new grommet, I just knew the damn thing would leak to, anyway easy fix if I could find the grommet, anyone know where we could buy one? and what the part number is?, preferably in Canada as shipping anything up here is killer duty/brokerage, someone must make one?, thanks