First two pictures are the “Big Daddy”. Second two pictures are the “Slim Boi”. The Big Daddy holds the G305 and three AAA batteries. The Slim Boi just holds the mouse.

Print settings I used in the pictures are 0.3mm layer height, really fast print speed, and lightning infill. Everything else was on default settings. I did add some small rubber feet to the bottom so that it doesn't slide on my desk. It could also be kept down with a command strip(s).