I have been looking for the original style cloth seat upholstery, I have found that no company has a reproduction like mine. Most have look a likes in vinyl but no cloth that have the 3 rectangular escutcheon that mine do..

 

If you have a local upholstery shop that can stitch it, contact these people for the bulk material. 99% chance they'll have the NOS material.
Largest Selection of Cloth, Vinyl & Leather Automobile Upholstery - SMS Auto Fabrics