So in many of my photos I have plastic boxes holding the cib’s and some carts. These are clear plastic boxes from retroprotection. They come in all shapes and sizes for systems themselves, game boxes, cart bags, and they even have protectors for non game merchandise like figures, cds and dvds, funko pops and more. Ive been using them for protecting some of my stuff for a few years now and never had issues.
Links for their online store and ebay. Some stuff that is sold out in the store itself may be on ebay and vice-versa: