I don't think you're gonna find any NOS leather or tire covers - they're both VERY sought-after, so there aren't likely any left on the shelves anywhere. My tire cover is one of the better ones I've seen, and it's starting to fall apart. I got some decent seats from a junker a couple of years ago, and they were pretty ratty up close. Even my brother-in-law's '93 in my driveway has a lot of wear on the driver's seat, and it was kept pretty well.
If you need a good leather BACK seat, there are plenty of them lying around. I have one to sell, and I think a few others here do, too.