I have Interior Innovations leather seat upholstery and have been very happy with them, going on five years now. Available in vinyl but the leather is worth $100 extra. Removing the old and wrestling the new onto each seat was not technically difficult but physically it was a bit of a work-out. You'll want a good set of hog ring pliers. People will suggest using zip ties instead. But those would have required that I cut a slit through the leather tab, whereas hog rings just pierce through on their own. I did use zip ties along the bottom of the back panel, because they lay flatter. You'll also need a good snipper for removal of your existing upholstery. I like these: www.amazon.com/gp/product/B000NQ4OYO.

EDIT: forgot I did a write-up about this back in 2018! https://forum.miata.net/vb/showthread.php?t=665682