Hi, I had a similar problem for long enough... I'm a left-hand-trackball user, the only model I find acceptable is a symmetrical model by Logitech which, of course, doesn't have a scroll wheel.
Here's my solution: Modern technology to the rescue! (*fanfare*)
Buy a €5.- USB scroll mouse, plug it in, place it somewhere handy, and voilá, scroll wheel
Plus, the occasional visitor can use the customary right-hand-mouse, or you can dual-mouse (or ist it mouse-duel?)
PS.: If someone can point me to a left-handable trackball with a scroll wheel
, don't hesitate to contact me
PPS.: Welcome to Atys!