Try looking in art supply stores. I got Itoya brand 
Presentation/Display Books in 11" x 14" for just over $10
and a 14" x 17" for around $21. I got these at Pearl Art
in Washington, DC, but they should be widely available. 
I tried Office supply stores with no luck. The Itoya books
are reasonable and the art supply stores should have others,
but I saw some that were over a hundred dollars which was
way more than I was willing to spend. Some of the dealers 
(like Usagi's House) carry cel books, too, and they are 
pretty reasonably priced.

Tsubasa