Mount to hold the switch and the pro controller together. Updated with v5 adding a latch to help secure the mount to the controller.

Honestly my design is kind of wobbly and the clip idea doesn't work very well. Check out some of the remixes people have come up with like:

https://www.thingiverse.com/make:506258 and https://www.thingiverse.com/thing:4806046

or feel free to customize the model.

Also, since a lot of people ask, here is where the 3D scan of the pro controller is from: https://www.tinkercad.com/things/1PSAeYNC8GN-nintendo-switch-pro-controller-scan