I've been a buyer's broker since 1991.
When you walk in, tell the agent that you are working with a buyer's broker. If the agent makes a fuss about the commission, walk out.
Call you agent. He or she can make an appointment for you at a time most inconvenient to the listing broker.
If his/her mother never taught him/her to share, you are not going to. There is no point in confrontation.