I'll try and find the Kodak photo's, not sure where they are at the moment. The Kodak 9x12 plate holder looks similar to the european ones, it's not like the Kodak film & plate holders for other formats. It's just the way the film converter fits in and is pressed that really differs.

Like you I can't see any need for pressing 9x12's I don't suppose they had laser cutters in Germany pre-WWII though

So far I've no idea how much they'll cost to make but as I'm not after a large quantity they'll have to be cut by hand, which is how many would have been made originally.