Where can I Find the Perfect Mouse?

Roar Lauritzsen asks: "After enabling scrolling with the wheel of my Logitech mouse in Linux/X, I find it indispensable. But holding the mouse in a natural grip while using the middle finger to scroll is quite uncomfortable, and soon after enabling this feature my hand started to hurt. To ease the pain I am now trying the Anir vertical mouse, but I don't think I like it. Personally, I think the thumb would be perfect for scrolling, but I have been unable to find a 3-button mouse (a must in X) with a wheel on the side for the thumb. What do YOU think is the perfect mouse, and where can I buy it? "