A couple of years back I bought some trunk gasket on the bay that worked well- don't recall exactly who. Had a fairly large line of stuff, so doubt he has gone away. Might try checking the ebay stores.
Also, seems Restoration Specialties had something that would fit- they have (or at least had a year or so back) a large assortment of trunk gaskets with to scale crossections shown in their catalog. The universal looked like it would be a good fit.