I know some of you freakazoid trackball people are still out there. (Don't email me to complain. You're the one with the problem!) But because I am not the type of judgmental person to point out what heinous, horrible human beings you are for choosing to use an alternative input method, I will do the Christian thing and mention that someone has made a product to address your disability, while also asking that you please leave the public internet to those of us who know the majesty of God's own peripheral, the laser mouse.
Oh. The product. It's called the Genius Traveler 350 and it's a portable USB trackball. I don't actually know how much it costs, but I'm sure the state will pay for it with doctor's approval.
Tiny trackball mouse gives travelers a new choice for mousing [Coolest-Gadgets.com]