Advertising Art

Does anyone know where you can buy Advertising creative work as art?

For example, I know Coke has a lot of their old advertising prints of old billboards and print ads sold as art. The other end of the spectrum is Absolut Vodka, has a lot of their ads show up on Ebay but they are just ads that people rip out of magazines. The legit sites that do sell prints only sell 8.5 x 11 inches.

Is there a place where you can by originals? At the very least larger genuine prints, not something that has been ripped out of a magazine?

People please leave your replies.

-A.B.
Inside That Ad
http://www.insidethatad.com/