a4 driveshaft u-joint size?

[Thomas Barbera]

Fellow audifans,
The center driveshaft u-joint in my sister's '96 A4Q
2.8 Auto is shot.  I'm trying to locate one in a
reasonable amout of time.  Has anyone found a source
for these?  Are all quattro u-joints the same size? 
What are the dimensions of the u-joint?  Any help
would be greatly appreciated.  Thanks.

Tom B.
'91 V8 5spd