Unless you can do the reupholstering yourself, you're going to be in for well over $2000 for new seat covers. Have you consider getting a pair out of a low mileage wreck?
For about $700-$800/
pr you can pick up ones that are pretty close to pristine and they'll likely be a better match for the patina of the rest of your interior. A quick search turned up some at oklahomaforeign.com (they have some eBay listings). Lots of 986s in bone yards and probably less than brisk demand for seats.