I just bought Emily a cute princess one at Wal-Mart for Easter. They also had Dora, Spiderman and Spongebob--maybe a couple of others, too. They were in the toddler girl's section (even the boy ones), on the bottom of the rack where the hats and bows are.
I also love the boutique brand Kidorable--they have super cute ones that look like frogs, ladybugs, etc.