Idea came after seeing @MWinkel 20kr Shopping Cart Key project. Thank you!
Just print them, attach to your keys to always have them with you, push the key straight into the carriage, unlock and pull the key out.
Every key has different diameter and thickness, similar to 1, 2 and 5 PLN coin.
Mine was printed in PLA, 0,2 layer. Other stiff filaments are gonna be ok.
The author hasn't provided the model origin yet.