There are a variety of ways you can do a bow. One of the vendors here sells the grooming bands and bows. I think she still sells supplies to make your own.
Dog Bows, Quality Dog Bows - Yorkie, Maltese, Shih Tzu - by BowBiz
She gives a $2.00 discount if you use the code: YTM2
If you look in the "Featured Yorkie Products for Sale" area you will see her ad.
She has some good info on her site for people just starting out using bows if anyone is interested.