Rethink the trackball. The problem generally isn't the trackball itself, its the fact that, on a standard arcade trackball, you need two hands, one for movement and the other for buttons whereas the mouse wraps movement, 3+ buttons, Z-axis in a nice package for one hand. Take a peek at ergornomically trackball and see what they offer you. The ball isn't nearly as large as an arcade and certainly not as durable but that doesnt seem to be your goal anyways.