Harry threw Ron a quick grin for the answer. He made a face at Hermione as she mentioned Polyjuice. It made sense, but it tasted vile. Not to mention the last time there'd been polyjuice, it'd been to make everyone look like HIM, and it hadn't ended well.
Harry saw the wisdom in it, though. He frowned, thoughtfully. "We could get your brothers or someone in the order to pluck a few hairs from some muggles and send them to us?" The twins would probably do it without asking many questions. "Or we could sneak out the tunnels for a few minutes - find a couple of people who are soused at the Hog's Head and grab a hair?" Which was probably safer than asking Ron's brothers. They'd go looking for someone really vile to de-hair just to make Ron turn into them.