Here's a link to a small pouch that could be attached to a backpack or even a key ring.
https://so-sew-easy.com/teeny-tiny-mini-zipper-pouch/
Great for little kids' treasures. There are lots free small pouch and bag patterns out there. Just google. Or maybe kids' aprons, library book bags, dolly blankets, cell phone holders, hair scrunchies....just off the top of my head...