Version 2 of my super simple wallet design. A bit more ressource intensive but way more heavy duty and now with very round edges, so much better for your trousers. Also it now stands on the table without wiggling around-

You will only need a rubber (hair) band and your are done.

It features a space for your coins and some paper money, since in many countries there are still people not accepting cards.

This design should be able to hold 8-10 cards, I don't think you will need more but let me know!

Protip: Scale to 5000% in Ultimake's Cura. Original size should be 91x63x20,88 mm.