Ball cups yeh, the black plastic things that pop on over the pivot balls. As for where, and how much...Dunno man, I still haven't upgraded to turnbuckles on mine. Next thing I plan to do. You'll find them or someone will know. Graphite dust at a hardware store, but don't worry about that, it's not urgent.

Ask at your LHS for ball cups, I assume they have HPI stuff??!

Take your truck with you!! Maybe this isn't the problem after all, but the way you describe it, it sure sounds like it.