Had the idea of storing my Raspberry Pi 3 B+ in the small tray that came with my Ender-2 Pro. I couldn't find any existing designs, so I created one using Fusion 360.

I wanted to be able to print this with no supports, so it was designed to be printed faceplate down without any supports. To achieve this, I had to separate the back walls from the main tray. The back panels slot in, though you might want to use a drop of crazy glue with light clamping pressure to secure it.

If you are printing this on an Ender-2 Pro, you will need to set the skirt loops to 0 to avoid going off the build plate.

I used 100% infill, though, I am sure it would work just fine with less than that as the whole model is mostly walls.

The fit is a bit snug, so you might want to sand down the sides a bit to make them smoother. I personally didn't do any post processing and put it in as is.

Edit 12/16/2022: I uploaded a modified version of the tray for use with a Raspberry Pi 4 B+; however, as I do not have one on hand, I am unable to test the fit. Overall, the two are very similar in dimension save for the placement of the USB/RJ45 ports on the front. If you decide to try it out, please feel free to let me know how it goes and I can make any corrections necessary.