Left handed, what about a game pad ? Novatech have a Belkin Nostromo N40 USB Game Pad @ £14.93 plus £2.10 p & p click here
Amazon have a Saitek ST290 @ £12.99
"The ST290 delivers unique design and styling to provide gamers with the winning formula at any level.
3-position Handle Adjustment to suit all hand sizes. Adjustable Palm Rest and central level throttle for left- or right-handed gaming"