This is a remix of Emotiva's "Shift Knob with Mazda Batman Logo M10x1.25".
I really liked his design but the automatic shift knob on my 2006 (NC) Miata uses a M8x1.25 thread pattern instead of a M10x1.25 like the manual NB Miata he deigned it for.
All the files are the same as his except I added an adapter to make an M8 nut fit into the M10 sized slot his design has. I also added a piece that press-fits into the base to give it some extra length so it does't look funny on an automatic.
Be sure to pause the print of the "MazdaKnobMain" file part way through so you can insert the M3 nuts. I just used the "change color" option on my Original Prusa i3 MK2S.
Also, you should also probably flip the "MazdaKnobBase" file 180 degrees so you don't need as many supports.
0.1 for the main part and 0.15 for everything else.
After printing, the M3 nuts should be encased in the main part of the knob.
Use the "M8 to M10 Nut Adapter" to make your M8 nut fit into the M10 slot between the main part and the base.
Then, secure the base to the main part of the knob with M3x25 mm screws.
Finally, press the "MazdaKnobAutomatic" part into the base. It's a very tight fit so you might have to put it on a table and whack it with a rubber mallet to get it all the way in.