Ive got a pair of these available, which were original to the 91BRG, 92B&T, and several M-Editions. Will fit any manual Miata across all four generations.
For the particularly detail-orientated, these have the threaded plastic base that Mazda used from 92 onward (the 91 Evo had a threaded metal insert with redundant set screw capped by a rubber base).
The OEM threading is the key - the universal Evolution model sold today has no threads, only inferior set screws, which will never hold the knob in place securely.
Youll notice the knob pictured on the left has the original rubber ring around the crown, which is nearly impossible to find now - most melted long ago into formless black goo.
The fix for that is to scrape the rubber out and replace it with o-rings, which is what Ive done for the Evo on the right. That one also has a couple very small enamel nicks on the crown.
$99 for the original rubber version, $69 for the o-ring version - first buyer gets first choice. Ill throw in free shipping for buyers willing to pay via PayPals f&f option.