Adafruit just updated https://www.adafruit.com/product/881 the seven segment LED backpacks with STEMMA QT connectors, and that prompted me to pull out some of my old ones and see about building them a case. It should work for the new versions that still seem to use the same mounts.
Files at https://www.thingiverse.com/thing:5551598 It should be easy to carve off single 30x60mm holders if you have fewer displays, or want to drop them into individual windows in your own case.
The backpacks fit into sockets in the faceplate and are secured by plastic pins you can melt with your soldering iron to hold them in place. The faceplate fits into the stand, which has a pocket to carry a half size breadboard.
