IMHO, the best pointing device EVER is the original Logitech Trackman Marble:
The three full-sized buttons is what I love about this trackball. Right clicking is meant to be done with your ring finger!!
If you MUST have a scroll wheel, then the Logitech Trackman Marble - Wheel is a good alternative (and these, if you can find them, sell for over $200 now days):
Unfortunately, the only thing close that is available (to my knowledge) for sale is the latest iteration from Logitech, the current Trackman:
It's decent, but is not a true three-button device. (no button for your ring finger unless you squeeze your fingers together)