As far as I know the only place to get the button as opposed to the sticker is at the hotels. Last year we stayed the night at Grand Californian for my daughter's birthday (actually the night we stayed was for the CM holiday party and her birthday was the next day, so with the great rates they offered for the party we stayed the night to be there on her birthday) and go the button, balloons, etc. You should have seen how many balloons we got, it was great. She even got an autograph picture. I think that one was Winnie the pooh, and the mickey one we got in the park because she got a bee sting while waiting for a show. Anyway, at Guest relations you get a yellow sticker (both DL and DCA) at the plaza gardens birthday celbration you get a white sticker, and at the Hotel you get a white button. I don't know if you're not a guest if they'll give you a button or not, I've never tried it.
Donna