I believe "Great American Gunstocks" has several different stock patterns that will work for the intermediate Mausers. I do not remember their web address, but if you do a Google search for "Great American Gunstocks" their web site will come right up.
I had a custom 7x57 built on a Yugo action. The 'smith used a B&C stock and did about $350 of modification and bedding to it in order to fit it to the action. Nobody makes a drop-in. I still may have the only synthetic stocked Yugo around.