Who sells these??

[gonzalo medina]

I read in a tech page they make plugs for the gas tank outer rim. I removed the aux tank. And now have this circle to cover.

[FORDification]

I know they're available, but I can't tell you from whom....or at least they WERE available at one time. You might have to spend some time contacting the NOS parts houses and see if one of them can help you out. You might luck out, I wouldn't think one of those would be something for which there's a large demand.