Nice score!
I don't know the specifics unfortunately, but I would think most of the standard large bore caps/covers would work in those. Yes, the wheel manufacturers made their own labeled ones, but most of them were the same shape and size from company to company, with just the different label.
Might even have been made by the same company and just private labeled, so to speak.
But that's where it ends. You should measure your bore opening to be sure of it's size, but someone will come up with a style/part number for you I'm sure.
Are you going to refurbish them? I've been hearing a lot about 'wheel acid" lately and someone just recently posted up how they used it on their aluminum transmission housing with good results.
Others have had their aluminum wheels polished with great results too. Not too expensive either from what I remember.
Paul