How to map a donation/payment box?

Hi there,

I want to map a donation/payment box (German: Spendenbox oder freiwillige Kasse) where you put as much money inside as you feel the attraction/toilet/parking/playground/… is worth. I was looking at “how to map a” wiki page, I searched the wiki and taginfo, but found nothing really suitable. It’s neither a shop nor a vending machine nor is anyone required to get a ticket. Any suggestions?

Thank you, Georg