96 chevy lumina front strut problem

Replaced front struts, and ball joints recently, was good for a while, but now you hit bumps you get a thump. we know strut needs to be replaced on drivers side but the chevy dealer said to also replace the strut bearing. The repair book (Haynes) doesnt mention the strut bearing. Where do you get at this and replace it? another term may be "strut bearing plate insulator and bearing" ...Just trying to shorten the search time

Yes the strut mount/bearing is the usual reason for the thump, look at the parts and repair info at autozone.com