I would definitely not reupholster them for around $800, unless you have money to burn. You're much better off doing what KenCopperwheat said and try to find some on those forums listed, ebay, and maybe you'll be lucky enough to find someone locally.
On second thought, you may be able to fix the problem yourself. Post on other E30 related forums and see what others have to say.
Also, check out what other aftermarket seats poeple have been installing in their cars. Most are worth installing.
Good Luck with that.
BTW, out of curiousity, what color are your seats?
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