I have Parkinson's disease and I have tried unsuccessfully to use a game joystick as a mouse I:could not configure the software available in Linux to work to my satisfaction.
During some recent research on the Internet I came across a reasonably priced 3 inch arcade trackball that I can build into either the desktop or make a simple box to house it and install it like a keyboard tray. It has four buttons and should, from the information I received act just like a normal USB trackball or mouse.
I intend to set it up so that one hand controls the mouse and the other hand controls the buttons.
I will add more information as I progress.
If anyone would like information about the trackball please let me know
Joe