Lots for sale in the USA but you will suffer an import duty.
You could change to later forks from another series, but as well as a new triple, you will need a new front wheel and speedo drive & clipons.
There are some half decent 600SS forks (brake hose rub and chrome pitting) on Ebay UK, I think the 900 internals might fit? I'm sure Kev (Skidlids) will know the answer to this one.
http://www.ebay.co.uk/itm/Ducati-600...-/282005826011 OR
There is a UK seller with a brand new stanchion (1 only) here:
http://www.ebay.co.uk/itm/NEW-OEM-Du...-/401016937083 Good luck