This is a a game cartridge for the RetroFlag SuperPi case. I based it on the SNES Mini cart designed by Tig3rch3n (https://www.thingiverse.com/thing:2561012 ).
Unfortunately it seems that the official SNES mini cart is slightly oversized for the RetroFlag SuperPi, so I used the model above and rejigged it a little to suit.
I attached it to the cartridge cover on my case using 2 small self-tapping screws, though you could glue it on just as easily.
I designed a label for the cart, based on one of my favourite SNES games, Super Mario World. I thought it would have been easier to find a copy of the label online, but it seems that there's a lot of scalpers out there trying to sell them.
I might design a couple of other versions if there's enough interest but for now, there's the Super Mario World style one in there. If you don't have sticker paper, you could print it on photo paper and overlay it with Celotape to give it some durability.