Correct Wing Nuts

I have been noticing at shows I go to and around, what wing nuts people use on their air cleaners.
I have been seeing not many correct ones out there but I see in a book I have the correct ones.

Does anyone know of a source for re-pop correct ones?

The ones that go on pie tin set ups seem to have a wider base area on the nut than the later ones that are correct for the painted type air cleaners. (72+) which still have a wider base area on the nut than a standard hardware store version

Like this?
It's cupped instead of generic flat.

wingnut.jpg