The upper one will be difficult to reproduce without a mold. It seals the flat splash foot panels to the upper dash. I would take pieces of cardboard and a hot glue gun and try to replicate it - inserting the gas tank as a guide for the front curves. Then coat it with resin and fiberglass cloth (maybe 3 layers) make the piece. OR contact the guy in Sarasota FL that has a complete set of CMC molds and see if he will make one for you. (His contact info is at end of his Miata Speedster build article - https://www.rcnmag.com/garage/...-based-356-speedster )
I saved this link years ago-