Kensington Orbit® Optical Trackball Mouse from Posturite
Kensington Orbit Mouse - Wired Ergonomic TrackBall Mouse for PC, Mac and Windows with Scroll Ring, Ambidextrous Design and Optical Tracking - Blue (K72337EU): Amazon.co.uk: Computers & Accessories
Kensington Orbit Wireless Trackball with Scroll Ring Review – MBReviews
Kensington Expert Mouse - Wired Ergonomic TrackBall Mouse for PC, Mac and Windows with Scroll Ring, Ambidextrous Design and Optical Tracking - Grey (64325) : Amazon.co.uk: Computers & Accessories