Aavid Thermalloy's P/N 552507B00000G looks real close to original. I don't know where you'll find this in your neck of the woods, but perhaps have your favorite electronics supplier see if they can acquire some.
I got a lot of 5 of them off eBay US just now for about 13 bucks. I'll post back once they arrive, and I can ship you one if needed.
Thanks for the pointers with the heat sinks John,
I already have the one from Futurelec - it doesn't quite fit as every second 'finger' is offset causing it to touch the surrounding components. I am going to try and heat it up and see if I can straighten and re-bend the fingers to make its footprint a little smaller - but I have a sneaking suspicion they will just break. The one from Aavid looks a little more promising - I'll grab one if the other option doesn't work.
Looks like that driver board requires a MAJOR rebuild - this isn't a bad thing as they cause a lot of resetting problems in this era of machine anyway.
Yes Mike I think I definitely got the 'Project' I was after
Oh well, I wanted a challenge, so I'll chip away at it and see how I go. At least I know if I get totally stumped, there's plenty of help available here