Hi Spedmetal,
I bought it from these guys.:
http://www.consoleparts.co.uk/ps2parts.htm
The one I got was the top one:'1 X KHS400B £23.98 Original SONY'.
The package is actually shown in the image at the above address. It was labelled as a KHS400B on a sticker on the side of the laser so it looked pretty good.
Is there a different type that I should have bought ?