To my knowledge, studios are not printing extras for the public and most of the studios are trying harder than ever to put a lock down on posters escaping their control. I know Fox and Paramount used to let you buy runs if you bought enough, but those days are gone. There is not an endless supply of newer titles so folks don't believe the printer is always on for whatever people want.
There were reprints on Avatar, I would suggest you check the size and print quality on the one you bought.
I can confirm that studios can actually be pretty damn tight about what they send to theatres. We usually get posters in pairs, or three for tentpoles. That's it. Doesn't matter if they come destroyed or if we want extras for whatever reason. More often than not our request for more is denied. That, and lots of Sony and Fox posters still say "Property of X not for resale or reproduction" on the bottom. Obviously they're fully aware of the movie poster market, but they have no intention of theatre employees being able to profit from their product.
That said, they don't sell to the public. It's still a mystery to me where retail websites get them - I guess there must be some sort of deal. After all, I've seen official posters on Movieposter and whatnot that never actually make it to the theatres. The most recent being the first teaser for Captain America. The theatre version simply said "AVENGE" with no title, but there is a version of the poster that says "Captain America: The First Avenger". But that never made it to a theatre wall, or not that I ever saw.
