Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:5176048.

The Model 3 and Model Y no longer come with the rear cubby container under the arm rest.

I included some internal slots for a Samsung T5 SSD, coins, and card holders.

Card wallets can be found here: https://www.thingiverse.com/thing:3020290

The 1 piece version will need to be printed with supports. Alternatively, you can print the bottom and top version (top is inverted) without supports, and glue them together. I haven't tested the fit myself, though. I also have the internal bits as a separate STL which you can import along with the regular cubby if you want to do multi-material, or do fuzzy edges on just the main cubby.