microSD-Card-Storage for ExpressCard/34-Slot

I carry arround several micro-SD-Cards an as they are really easy to lose I was looking for a good way to store them.

I was inspired by the existing designs, but my thinkpad only has a 34mm Expresscard-Slot.
As there was no sourcefiles uploaded, I came up with my own build (and included my Freecad-File so you can adjust, if needed).