I've just bought one from e-bay USA for $250 dollars.
The amount hasn't been deducted from my bank account yet, but I reckon that's around £140 to £150.
It'll take a week or two to arrive mind, but I don't mind. It's my spare.
My current one has been on the go since September 2005 and has had a good battering, so a spare would be a good idea.