I use this one at work. The trackball is still worked with your thumb, but you still use your index and middle-finger for the buttons and scroll-wheel. It is wireless.
Logitech used to make a wired version of it, but it has been discontinued. Demand for the wired version has caused its price to be inflated to a ridiculous level. From what I have read, the wired version is slightly bigger and some people say it's a bit more ergonomic. I don't know, I've never used it.