UNIONDALE - ? Cops are searching for a robber who held a gun to a woman?s head in Uniondale.Investigators say two masked men walked into the MetroPCS store on Uniondale Avenue yesterday afternoon. Cops say one man put a gun to a customer?s head and forced the freightened woman to lie on the floor. A second man demanded money from the employees. Cops say one worker filled a bag with cash and the two men took off with the money.