RZ covering appears to be molded material into shape, This is not a piece of flat whatever that is cut to shape then shaped as needed at glue on. I have not ever seen body covering replacements for RZ, it appears as it could have only been done under controlled production environment.
Seems like you have two choices: write to those who do re-covering jobs (camera leather is one of them, some camera repair shop do that too), if they are willing to take on this odd one, or find a material that can be cut to shape (make a template first with paper so it molds into position as neatly as possible) and apply it yourself. I think end result will probably not be looking much better than the current naked section.