Police are searching for a man they said robbed a Bridgewater Credit Union yesterday. The suspect told a teller at the Clay Street branch that he had a firearm, although he did not show one, said Mike Bowes, a Quincy police dispatcher. The man was given cash along with a dye pack. The money was found nearby. Police said the man was black, in his 30s, about 5-foot-10, wearing a black leather coat.