got some acme upholstery covers from rockauto for my 76 regal... worked out fine. just had to ask a local upholstery guy to split the front bench seat part.
Purchased the complete interior for my 71' Skylark, headliner, door panels, front bucket seats and back seat cover. This is done by PUI, Parts Unlimited, Inc., LaGrange, KY. They do not sell to the private individual but can be bought through the Parts Place in Dekalb, Ill. I bought the front bucket seats thru Ausley's Chevelle in N. C. but it all came from PUI. The bucket seats and back seat cover is done in the Buick Stitching.
Skylark interiors are remade. Legendary and PUI make skylark stuff. Legendary is better quality. The OP is asking about Century interior which I do not recall being reproduced. But you can still purchase the original material from SMS and have the seats redone to factory style locally.