Try a hour hour photo lab.
What I have is a changing bag for those one hour film and printing shops. They use the bag to load paper into a cartridge. Its hugh! It has four pegs to hold the bag erect with two arm sleeves to work with. It folds in half for storage. I use it for my 8x10 I have space for several holders, a box of film and another box to load film into.
Check out a one hour shop, ask to see if they have this bag and you'll know what I mean.