I tried one of those, but you can only use them with left or right hand and the wheel still aggravates my wrist. Swapping from left to right seems better. I also add in a little weight training and I don't have any problems.
Did you check finger operated trackballs? They are symetrical and can be operated by both hands.
Examples: Kensington Orbit, Kensington Expert Trackball, GameBall trackball, Logitech TrackMan Marble, X-keys L-Trac.