I don't collect seeds to outlive humanity, lol, just to give me a gardening fiddle-fix in the dead of NY winter.
I use paper envelopes cut in half and stored in a 3x5 index card box (because that's what Meets humidity and storage needs that I found at the dollar store, lol.)
If you were creative enough to design something simple, cheap, small and attractive (say something that could stay on a kitchen windowsill) I'm sure you'd find a market, especially as a gift item for gardeners like me, but you'd have to keep it under say $10, because seeds are cheap, they do have a limited shelf life, and storage space is at a premium in all our lives. I don't know if it's possible or worth the effort if you're doing it for any reason but self gratification.
There's no way in the world I'd sacrifice the space to put 40 pairs of shoes on the back of a door, or even a hook for a robe I used every day to save seeds that would total a volume of maybe two tablespoons, and something smaller might be tough to get the seeds into pockets..