I tried some boxes I found online but could not find one that fit my need ...
I liked the "Playing Card Box" by "mkoistinen" so I designed my own version of a Uno Pocket Card box based upon his Playing card box.

I later added an H2O-version (same box but larger) since I had that version as well and it seemed the cards for that version are larger. As some people mentioned their UNO-version did not fit the box It might be that this box fits their size cards.
The Uno Pocket version has cards sized 55mm x 81mm (stack size of 31mm) and the Uno H2O version has cards sized 56mm x 87mm (stack size of 35mm). I also changed the clearance to 0.2mm as the clearance of 0.5mm made the box fall apart when it was picked up.

2020-12-07:
Made yet another version measuring from an "official/regular" set (in Belgium at least) (cards measure 56 mm x 87 mm x 32 mm)

Print instructions

easy to print without support ... if you need support, you're doing it wrong ;-)