What breather?

["Erlandson, Paul (P.W.)" <perlands@ford.com>]

Okay, here's a stupid question ...

I have a 63 Buick motor, and I have bought the Offenhauser
finned valve covers for it.

I cannot, in all the places I've checked, find a breather cap
to fit these.  Most I have tried will not go down far enough
to reach the breather hole, as they hit the fins first.

What breather fits the Offy valve covers, and who stocks it?

Thanks,
Paul Erlandson
Royal Oak, Michigan