Hi Ryan, I think that Rowan is the only one that makes the kit, I got mine straight from Rowan, reasonable postage and here in a week.
http://www.rowanastronomy.com/productsa1.htm
I did have a look at buying the individual parts but they are not that cheap and when you add the lot up the kit is a good price and ready to go. There is an optional pinion extractor tool, I got mine off easily by leaving the motors in and levering the gears off with two flat screwdrivers, one on each side of the gear.
Pretty easy mod and defiantly improves tracking.
Rick