I know you said you wanted a wheel, but...
I wasn't so sure about the Kensington scroll ring, but I'd lost my old Logitech marble mouse and wanted something small and left-friendly, so I gave it a shot. Now I wish I had one at work, and I wish there was a way it could be incorporated with mice. The wheel is a repetitive-motion nightmare by comparison. I think of it this way --
scroll ring : scroll wheel :: bicycle : kick scooter
Consider trying a scroll ring. It's smooth, speedy, accurate, good for short and long scrolls, and lends itself to different techniques.