Hi Bob,
I went ahead and contacted John. He says he can have them made. Here is a link to his page with metal parts he's had made before:
http://www.amptechsystems.com/items_for_sale.htm
I think he can make one that is an exact duplicate.
Next step is getting him a sample from which to get an estimate. I'm in Colorado now and can't send one for a month, but perhaps there is someone out there who could send one?
The model 5 uses the same cover, and I think the 21CT55 may be the same.