CANOPUS Magnetic Sheets with... https://www.amazon.com/dp/B07V59GVXX?ref=ppx_pop_mob_ap_share

This is what I use. When you use magnet sheets you need to get thick ones like this or they won't have a strong enough pull to hold your models. You can use any plastic containers that fit the dimensions you need, but you want a stronger glue to attach the sheets to the container. I use gorilla glue for this.