who does

In the example at top, "who does" means "who works on Volkswagens". You can imagine that the conversation went something like this:

A: Hi, I have a problem with my '79 Volkswagen bus. Do you work on those?

B: No, I'm sorry, we don't.

A: Oh, OK. Thanks anyway. You wouldn't happen to know anyone who does, would you?

This phrase appears in these lessons: