Also consider the 4 rear lateral control rods. (That's what Toyota calls them.) It's usually the rear one of the 2 on each side that goes. The bushing goes out on them causing a clunk. That may be what the shop is referring to as track rods. You can test these out yourself rather easily. Just jack up the rear of the car. Now grab each rear wheel at 3:00 and 9:00 and try to see if there is any side to side play. If there is, chances are you will also hear the clunk noise. To my knowledge there are no replacement bushings available for these, even in the aftermarket.
Mike