I got this card protector as a gift from my bank and I am very happy with it. However, I was not able to carry any bank notes with me and I am not comfortable putting the notes loose in my pocket together with my keys. What I needed was a money clip but I could not find any clip which I could fit on the protector. So I created one myself.
First I printed it with PLA but it deformed and could not hold the notes. Now I have printed it with PETG which is a lot stiffer and this looks very promising. The dimensions of the card protector itself are 62mm × 8,5mm as shown in the drawing below.
A 3D view of the drawing
The 3D view and the photographs are branded, but I placed an unbranded version on Thingiverse.
Contact me if you have any questions or if your card protector has different dimensions!