You would probably do better to contact the producers of the assorted shows, like Disney, the Nederlander Organization, Dodgers, etc. You're not going to get much in the way of playbills or posters by going to box offices.
"If they can get you asking the wrong questions, they don't have to worry about the answers." Thomas Pynchon, GRAVITY'S RAINBOW
"Reality is that which, when you stop believing in it, doesn't go away." Philip K. Dick
My blog: http://www.roscoewrites.blogspot.com/