Answer: Carmen's House of Flowers
This was the shop which Andy had phoned when he wanted to send flowers to Sydney after the State Dinner. Then, when he was in the motorcade and had to ring Sydney to break his date with her, he suddenly spotted the shop and told the driver to stop so that he could 'hop out and get her some flowers'. When Lewis told him he couldn't just 'hop out', Andy replied, 'You think there's a florist who's planning an assassination on the off-chance that I'd be stopping by?' And Lewis said rather uncertainly, 'It's possible.'