Sounds like you need some kind of community shop, that sells/loans things you want in the way you want it.

You don't need the clothes that society tells you you have to wear at different events, just need 50% of people not to care.

Good luck making the selling of individual envelopes commercially viable!

That said, totally agreed there's a gap for bringing the "sharing economy" to things people buy but rarely use (lawn mowers, leaf blowers, pressure washers, etc.)

I needed 1 envelope last month. It was 1 PLN (0.3 USD) at nearest street shop (kiosk). I don't think they lose money on that. I also bought a pen there for another 1 PLN.

They mostly sell cigarettes, newspapers, chewing gum and tickets, but they keep some envelopes, empty DVDs, pens, lighters, etc - it's not going to expire and they have huge markup, so why not?

Are there no small shops in your country?

I guess you only have superstores around. I just go to the newsagents and buy one for some cents.