SZ seat builder
Camillo Scaduto in San Diego north county has built these before, and may have fixtures or drawings. He had been working at Alan Taylor Restorations in Escondido but last time I checked, was working for a defense contractor in San Diego.
Camillo might take an order for some seats anyway. I will try to locate and send his phone number to you. Others on the AlfaBB may have his contact info as well.