Craig,
You'll get better local help if you sign your post with some location information.
Assuming you're an INA member, you can contact the original Nonsuch rigger, Mike Quill (click MAINTENANCE on the MEMBERS tab on the website). He may still have wedges and boots that he's selling, and since he's retiring from his business could certainly tell you the material and measurements and/or his sources of supply.
You can also easily fabricate them yourself out of hardwood or a strong plastic such as delrin, or have a local shop do it for you. You can get the measurements by finding a N30 neighbor who will let you measure one of theirs. If you're an INA member, you can find folks nearby using the Advanced Search capability via the DIRECTORY/REGISTRY page accessed off the MEMBERS tab on the website.