Where can I find Shimano jockey wheels? I have a Shimano RD-M510 rear derailleur that needs both jockey wheels replaced.  Were can I find them for this older unit?
Jerry
The compatible part is SHIMANO RD 5700 and the part number is 5XH9812. The set come as a pair and is available at a number of places such as Chain Reaction Cycles and Wiggle.

The only thing to ensure if using generics is that they are the right chain size.