Tim, other than having Mike A., Paul B., Dave G, Jan K. or one of the key stock makers fabricate you a custom walnut or exotic wood stock, the Custom Stock from England on my Diana 52 looks, feels and fits very well. It is a nice stock and added better hold control of the rifle with the thumbhole design. That's a subjective personal thing.
Like the other gentleman said, they are a bear to get a hold of, phone number only and no email address. If memory serves me correct, Pomona Airguns was a dealer for them at one time. You'll have to check.
Jim Macarri has a nice Diana 54 stock in walnut and Paul W. is doing finishing work on these right now for a very resonable price including stippling the hold areas. He did my walnut Thumbhole Sporter and I'm very satified with his work. You can get it tuned the same time it is there.
If and when you satin black rubberize texture coat the one you have, please post or email me a photo.
This is the site for CS in England:
http://www.aocc61.dsl.pipex.com/products.htm
Best regard and God bless,
Jon - San Diego