Miata Seats fit. I've found them to be in the $150 to $200 range used. 2000+ Seats are thinner. Cloth inserts keep you cool in the summer and headrests can be fitted with speakers. Problem with other aftermarket buckets is that they are too wide.
Can someone please repost the Search the Junkyards Link. I had that link and managed to forget where I saved it. You can input your zip code, Make and Model, and desired item, yes there isa category for seats, and the link will search all junkyards or should I say recycling centers by distance from you. I looked in OH and found Miata Seats at several junkyards < 1 hour away.