Skadis mouse cup, super straight forward. Fits USB dongles inside the cup. Made since all other solutions were too unstable, so a cup with curved opening and a dongle holder inside was the best option functionally and not too bade aesthetically.
Requires the Skadis Universal Hook found here: https://www.thingiverse.com/thing:2853261/files
New version with external dongle holder was made. Makes it even easier swapping in and out wireless mice that don't have an internal dongle holder.
The author marked this model as their own original creation.