I have made a custom slim case for my external SubGHz module for Flipper Zero. There are various types of SubGHz modules for Flipper, so please check the link below or the photos to make sure it fits yours. I have printed mine using a transparent PLA, might try transparent resin later, be sure to post your results. The print consists of 2 parts that fit tightly together without the need of using any glue or screws. No supports needed. I recommend to shorten the module pins on the back to be flush with the soldering so that you do not need a cutout on the back of the case, you might need to do so as well to fit it well ;)

C1101 SubGHz module that I am using: https://www.ebay.com/itm/155852886785

The author marked this model as their own original creation.