I use the scrunchies also. I redo Rosie's topknot in the morning and before we go to bed. I "loosen" it at night to give her scalp a break. I purchase them at Walmart in the baby section and from BowBiz.
Scrunchie Fun/PonyOs: Top Quality, Handmade Dog Bows - Yorkie, Maltese, Shih Tzu - by BowBiz I think the scrunchies are the best thing for growing out a topknot. Rosie has one everyday!!