Up for sale is a Moddiction Anvil 2 Shift Knob. It is in excellent condition and came off of my NC. This should fit all Miatas.
Description from the manufacturer:
Anvil 2 Textured Black Stainless Steel Shift Knob.
101.25 thread pattern
Textured Black Powder coated finish.
Weighs in at over 400 grams.
Height is approximately 2 1/4
Fully countersunk to lower shift knob height 1 or more.
Height adjustable for 101.5 and 101.25 shift levers.
Made from 316 Stainless Steel.
Price is $75 Shipped or best offer.