I don't think us left hander's have many options.
Razer - DeathAdder Left-Handed Gaming Mouse - Seems to be the best i can find, with limited extra buttons (2 i think)
Most mice with many extra buttons tend to be right handed, I've seen a couple that can be used with either hand that seem alright, But I'm likely going to buy the Death Adder soon unless somebody has another good suggestion
Any help would be great!