Print your own wallet!

Originally designed for semi-flexible filaments such as TPE (used for the red wallets in the photos).
The Mini is printable in stiffer materials (white PLA used in first photo). However, this gives a very tight fit for the cards so you might want to scale it up with a few percent. If printed in flexible materials such as TPE there is no need to scale, cards should fit perfectly as is.

FlexWallet Full
Best for those of you who use cash a lot. It has 6 card slots and a bill compartment fitting bills up to 187x74mm without folding; if you use higher bills, just scale up the Z axis when printing - The card slots will still be usable thanks to the grip area made for easier card handling

Flexwallet Mini
Best for those who rarely use cash and/or want a wallet as small as possible.
It has 4 quick access card slots, each holding a single card. Additionally there is a middle slot that can fit 3 cards and/or emergency cash (folded). The middle slot is slighty deeper in relation to the top edges to protect bills and rarely-used cards.

There are two versions of each model:

Skull contains the skull logo from Quentin Tarantino's Death Proof (painted on the car driven by Kurt Russell).

Clean is completely plain, add your own logo, name or phone number as you wish.

I have used both the Full and Mini versions for a couple of week each, there are no signs of wear and tear so far. The contents stay in place and I never worry about dropping cards or bills by mistake. Both models go nicely in the pocket, especially the Mini.

2016-10-13 - New design
After 8 months of daily use, my Mini is still in excellent condition, although slightly dirtier.
I still wanted a change, so I made an improved variant and printed it with wood filament! Check out http://www.thingiverse.com/thing:1825738