Think I got mine from a firm called SGS?, cheaper than ebay, and quick delivery.
There is a thread on here somewhere, that's been dug up and revived a few times, I'll see if I can find it, but may not happen, as I'm on a caravan club internet connection (barely!!).
EDIT:- Found another thread about them, here's the link.
http://www.cargasstruts.co.uk/product_info.php?cPath=26&products_id=1571