There are enhanced containers used for storing military weapons. They have a gas treated interior, I have one. They are plastic bags essentially.
Buy some NOS gaskets and preserve them before they get ruined. Some NOS is showing its age soon if not preserved. Those wrappers don't stop everything and they normally look pretty tired.
What would it really take to create these things? Cereal boxes some goo, a steam-roller and a cookie-cutter?