This simple plate works for both v1 and v2. It has no support or screw inserts, so not ideal for hotswap builds, but does the job.
This is the basically the same plate with a few supports placed where the mounting holes are. I have not tested to actually screw this on, Im just using it without screws: left plate with supports right plate with supports
This is a case I made, very compact, almost no empty space inside: https://www.thingiverse.com/thing:6661648
Lots of pictures here: https://imgur.com/a/cheapino-2-case-R4ialST
A bit unfinished build guide for this case here.
TheMadClover made 2 really nice looking case options, one tented, and one flat, check them out here: https://www.printables.com/model/879047-two-case-designs-for-cheapinov2-split-ergo-keyboar
This is a VERY nice case with built-in support for tenting and a travel solution: https://www.printables.com/model/835134-cheapino-split-keyboard-case
This is a case for v1 with a simple tenting solution: https://www.printables.com/model/541536-cheapino-case-with-basic-tenting