You can buy circular plugs of all sizes, and many styles, online.
Some work desks have plastic hole cover with a sliding "door" to poke cables through. Great for using different controllers, thinking consoles, but anything really. Wonder if anyone makes them in your size?
A 3D printer would be great.
I can imagine using that trackball means whacking your hand into the screen a lot, at least with some games? Screen is very close to CP.