These are becoming very difficult to find outside of complete sets. I did notice a post on the Weight Weenies forum a while back showing that Shimano has been offering their newer e-tube rear derailleurs with a conversion module that allows linking them to Gen1 wire harnesses as 10 speed derailleurs. No idea on availability and the prices listed for the shops carrying them were pretty high, but might be worth contacting Shimano or asking your LBS to contact Shimano. http://weightweenies.starbike.com/...ewtopic.php?t=142606 Here's one listed in a Swiss shop. Swiss Franc is pretty much equal to USD:
http://www.rocky-bikes.ch/...Wechsel-10-Gang.html