Don't search for change the next time you need a trolley.

Attach this to your keys & all your problems are over (note: this may not solve all your problems).

The holder is best printed in PETG for flexibility, PLA will likely bend or snap when inserting or removing the coin.

I'd recommend a 0.1 layer height for the holder & slow speed with the PETG (~ 35mm/s). There are some tricky overhangs but it should print without support. My ender 3 does a good job with no supports at this layer height.

The coin is a 2 Euro size & can be printed in any material you like really, recommend a 0.2 layer height.

It is oriented face down for a smoother finish on the image side.

Once printed, the coin simply pushes into the holder & can't fall out. When you need a trolley, just pull the coin out of the holder & push it back in when you're done.