Neils,
I use an old Belkin mouse that's pretty big. 3-button and roller ball (that squeaks like a mouse). Belkin F8E813-BLK-USB. If you can find one, I'm sure they are pretty cheap.
The Contour mouse looks like there should be a size that you'll like.
I'm not as young as CATIAJim, and I've never figured out how to use mice with scroll wheels in the middle. They always seem to make my tree move when I touch the wheel!