Seat cover
If you have one thats remnants but mostly there, legendary may make a deal with you in using your old one as a pattern. Might be worth a try.
Else, find a good upholsterer to make a set. I have a friend in colorado (John's Auto Upholstery in Longmont, CO), who owns a '65 Dart 170 2dr and owns an upholsterer shop. I've seen him make some pretty original looking interior for a number of old classic's that 'no one' makes covers for. PM me and I can get you his business info if interested.