I recently discovered Autodesk Fusion 360 which, as it turns out, is super easy to use. It took me about an hour to get to grips with the workflow and design the case below for my RB435:
I didn't really bother with accurate cutouts for each plug but it's a snug fit and works well. I also didn't want to deal with six screws. Instead, I opted to extrude 3.4 mm diameter pegs which the PCB slots onto. The top part of the case fits "tightly" over the pegs and holds the PCB in place too.
In addition, I added two SMA sized holes at the back for when I add a WiFi card and want to mount a couple of antennas.
You can download the STL files and print your own: https://www.thingiverse.com/thing:2676707