Amazon.com: Kensington Pro Fit® Ergo Vertical Wireless Trackball (K75326WW), Black, 3" x 4" x 6.1" : Electronics
Amazon.com: Kensington Orbit Mouse - Wired Ergonomic TrackBall Mouse for PC, Mac and Windows with Scroll Ring, Ambidextrous Design and Optical Tracking - Blue (K72337EU) : Electronics