I think it depends a little on where you live. I bought mine from a retro game box store in Sweden (https://www.retrospelboxar.se/sv/?gclid=Cj0KCQiA1NebBhDDARIsAANiDD27gd2AfEanD3GXuLxu9BQZP6swREq1I1pyO0cqDI5xVO3_Z-mTHXIaAue3EALw_wcB). But I think Amazon may have some as well (e.g. https://www.amazon.com/Universal-Case%EF%BC%88empty%EF%BC%89-Genesis-MegaDrive-Nintendo-64/dp/B08Z2VJ7PT). But you need to get the cover prints from somewhere as well, and I'm not sure where to get your hands on those where you are at though.