At our school (secondary) kids are staying in their tutor room all day and teachers are moving from class to class. After three days of unsuccessfully trying a backpack, tote bag and plastic box, the solution dawned on me.
A nappy caddy!
Well, it worked better than I ever thought it would, and a few of my colleagues asked what it was. At first I thought they were taking the piss, but I played along and sent a teaching staff email out with the amazon link and a jokey endorsement disclaimer.
Now 7 other teachers have one, and the head teacher has offered to buy them for anyone who wants one/reimburse anyone who has bought one! Who would have thought!?!