One of the best sources for used parts there is:
http://www.roverguy.com/
If he says he has the part, he does. Unlike some places.
If your propshaft is ok, aside from the broken u-joint, and you have an Advance Auto near you, PDQ10005 is the u-joint you need, about $13 or $15. It's made by Neapco and is a quality u-joint. It's what I've been using for years.