There are like buttons already, but they don't go to your set-up-by-you page. I haven't found a way to merge the likedness of them with business pages. A url in a listing or announcement is all you can do. Etsy doesn't allow HTML modification.
Well, when I was listing items today it asked me if I wanted to post to my fan page. I just recently got the FB button under my banner for my FB fan page....