A business I work for has one of those fancy 'Like Us' decals on their window, and I finally got around to finding out just where they managed to grab it. It looks like Facebook had sent them out to businesses a few months back to help up marketing, but has since stopped production. For now, you can make your own with the file here:
"Quite similar to the “People love us on Yelp” promotional stickers you see everywhere, these eye-catching window decals in the shape of a speech bubble include the social network’s well-known logo, the familiar thumbs-up “like” icon, instructions on how to like the business via a text message to 32665, and the actual Facebook page URL of the business." http://reface.me/goodies/like-us-on-facebook-stickers/.