I needed a deck case for the non-standard size cards that cam with the game Letter Jam. Nothing available? So, I designed my own. But, having done it in OpenSCAD, with the program file I set it up so you can input parameters (length, width, height) to make whatever size case you need!

The STL file I've uploaded is for the Letter Jam size card deck. The lid is a little loose, so I use a rubber band to ensure it stays on. It is 1/2 mm larger than required to fit the bottom, but when I didn't add that extra 1/2 mm, working the lid on/off the bottom was next to impossible. Maybe changing it to 1/4 mm would be sufficient, but I was happy enough with it and didn't feel like another print.