Years ago, I had Coker MAKE me a Split Rim for my Series 80.
I sent them a detailed drawing of the rim, cross-section included, along with photos of it.
I also sent a photo of the locking mechanism.
The rim was a size that they did not make (width-wise), but they did create it for me.
It cost a few bucks, but they got a very nice one to me in relatively short order.
However, you may have already had this conversation with them.
Good luck and perhaps you need to scour eBay.