The Losi Molded Thrust Bearing with Hard Balls is part number A-3098 and lists for $5.00. I prefer it over the hardened carbide balls you can get from Losi; however, putting individual ceramic balls ($1.00/ball) in the diff and thrust areas gives really smooth diff action.
At $9.40, the McMaster Carr #7806K53 bearing set is almost twice the cost of the molded Losi unit.
The MC set may cost more; but, if Todd Hodge uses it, I assume they are better.
I have one XXX-S setup with all ceramic balls and the other with the molded Losi thrust bearings. Unfortunately, I have too many variables between these stocker cars to make a call one way or the other.