I may be late to the game on this topic but here goes. I froze a few supers this year because I had to wrap up extraction and move on to other things. My wife had a few clear plastic produce bags from the local supermarket which she called 'corn' bags because she says they're extra big and wide. The store puts them out next to the corn on the cob bins. Each one covered a super almost to the top, so I put another one on in the opposite direction, wrapped a few rubberbands around both and it was sealed off fine.