Mate, ive had i right nightmare with this part.
It seems that the only different tensioner is for the old style air con with the max and min buttons. All the others are readily available from any parts place.
The one thats availalable is a composite plastic material whereas the one i need is all metal with a completely different fixing and tensioning method.
Went to my local dealer (last resort) and they searched nationwide for one, but as the part was discontinued and not many valvers were made with the older air con apparently), they couldn't find one.
So my options were to wait until i could find a breaker 16v with my type of part on it or to go to a local engineering firm and try and get em to replace the bearing inside the metal pulley.
Should find out today if he's managed it and will let you know.
It did piss me off a bit though how hard such a simple part has been to find (i didn't find one). Im sure i would eventually but i cant afford to have my golf off the road for that long. Would be good to find out how many were made with my spec as its a bit off to produce a part/set-up that you cant fix.
still should find out today!