The file 'Nintendo 64 Cart Holder 3D Printer Model' is (stl) file type, size is 103.6KB.
UPDATE 2020: Now With a 9 Cart Version to fit on a standard Ender 3 Build plate.
Couldn't find any cartridge holders for the N64 that looked decent and offered a snug fit, so I made one. It holds 10 carts.