I kinda doubt you'll find the part you need in your local electronics shop, and its even harder to make a good soldering job on the esc as Castle use special high temperature solder- more likely to damage the esc and surrounding components through the heat.
As it is, there are a few good pictures around this section-
2244
T35HV
hard to make out, but thats what you're looking for, its in the bottom left of that picture, upside down. Maybe Castle can send you the missing bit, or you may be lucky and find it online, but I think you may end up having to spend the money to send it in and get it repaired...