That was fast! Just days after Sienna Miller reportedly gave DJ Slinky Wizard the kiss-off, the PDA-friendly couple was shopping for vintage (but never worn) underwear in SoHo. Our spies caught the Broadway beauty and the Brit disc-spinner (real name, George Barker) snapping up the old-style undies, a “Heart Print” crop top and other items at Only Hearts on Mott Street yesterday. “They seemed very much a couple,” said our snitch. “George was talking about how he was excited about their plans for the night.” Last weekend, reports out of London had Miller dumping the Slink-man because she wasn’t up for a transatlantic romance. “That didn’t look to be the case,” our spy said. And, despite seeming to be a bit behind schedule, Miller “was very pleasant and kind,” said our witness. “She left some pieces in the dressing room when she left and apologized to the staff for not bringing them back out to put on the selling floor.”