I recently installed OctoPrint on my Raspberry Pi so I could remotely control my 3D printer. I needed a good case for the Pi. I found one that allows me to mount the Pi to the 3D printer.
Raspberry Pi 3 Case for Creality Printers on Thingiverse
Here are my photos:
I'm having issues with my prints, so this isn't the prettiest case, but it's sturdy.
Update: My Raspberry Pi camera cable wasn't long enough to reach the back of the printer, so I moved the Pi to the front. I also wired up my Raspberry Pi's power directly to the Ender 3's main board so I didn't have to have an extra wall plug. This means that the Pi will turn on when I turn on the printer.
Update: The direct wiring approach does not work for me. I received under-voltage warnings from OctoPrint, so I had to go back to using a USB power supply.