Gasket for Fury passenger mirror 3586848?

[SeaFuse]

Hello - looking for a source of the mounting "gasket" for the above mirror. I do not see the gasket in factory parts books so assuming they were normally supplied with the mirror. Below pic of same mirror for illustration (72-73 Fury?). I see some A/b/E body mirror gaskets being reproduced but look to be a different shape than this one. Thank you!

 

[SeaFuse]

Bumping for assistance on gasket source . . .

 

['66 Fury I]

When I needed one, I cut it from the side of a black plastic pail. Is still serving well some 30 years later. Hope this helps. Lindsay