No idea if these work but they look interesting.
Wow, I've never seen one of those, and weirdly I want to try one whilst playing AsteroidsA couple of folk at work swear by this = http://www.3mdirect.co.uk/p-423-ergonomic-optical-mouse-laptop-pc-usb-large.aspx
Thanks peeps. I'll look into your suggestions. I already switched to my "wrong" hand years ago, and now that's getting bad too. I use shortcut keys a fair bit, but I still need the mouse for some things. I haven't any more hands to try. The gel wrist pads almost seem to make it worse - I'm after a totally different-shaped mouse. Might try the one Ffoeg suggests as it seems to be a median nerve thang...
Mac OS X (and all Apple computers and their input devices) has full multi-button (or multi-touch) support, always has.Use your "wrong" hand for a while. Swap over the buttons* and it's surprisingly easy to pick up. For a mind-bending workout swap over the direction but not the buttons.
And get used to keyboard shortcuts instead of mouse-clicking.
*I assume you use Windows and not Mac...