You could almost call this an "all-round" type of mouse. While most computer mice have two buttons (and maybe a scroll wheel), this one has four.
From Amazon
Kensington Expert Mouse - Wired Ergonomic TrackBall Mouse for PC, Mac and Windows with Scroll Ring, Ambidextrous Design and Optical Tracking - Grey (64325)
This product is also available at 4 unverified merchants.