I used these people when I rebuilt my rear wheel (I had more than one spoke broken, and most loose, so I did the whole thing):
Central Wheel Components Limited
Great products, but best to send them a sample of what you need, as they don't seem to keep specifications in stock for rare bikes like the XT

If they have the specs there, they will be from my bike!
Loads of stuff in the catalogue, complete with price lists etc.