I remixed a file i found at: https://www.myminifactory.com/object/3d-print-cassette-case-inserts-for-gameboy-gameboy-advance-117847 when i made those ones the holders would snap off, probably just due to the filament I was using (PLA) but I figured the Cassette hold it pretty well when not held down. I added my own side holders and they worked perfectly. Hope this helps you to want to make your own cassette case GB Cart holders, I tried to post a link to the forum , but thingiverse blocked it, just google gameboy cassette covers and it should be the first reddit result. make sure you size them down to 10.32cm width and 10.16cm height and share your prints on here!