Ah man what a shame, I too went looking for it around d23 and was unsuccessful. When I spoke to a cast member she told me something about the company who owned the rights switched to new owners and they are attempting (along with many other paintings) to put them back into Disneyland :/ Darn legalities. Guess we'll have to wait it out and see.
But if anyone else knows someone willing to sell their personal piece or a company that can sell it please do step forward!!
My Mom Beverly worked in the Disney Gallery from its opening to 2002. She is now selling her collection which includes lithographs and other artwork from the early years. We have 3 signed Herb Ryman lithographs of "New Orleans Overview" as well as a reproduction print of the "Suggestion for Lighting the Central Plaza" signed by Lucille Ryman Carroll for Herb Ryman.
Feel free to contact me for prices or if there is something particular you are looking for.