A5 Paper in the US

Does anyone have a recommendation on where I can buy A5 paper (or even
8.5" x 5.5") paper in the United States?  I've checked with Office
Max, Office Depot, Staples, Viking, Betty Mills, etc.  I can't seem to
find anything in a "half" page size anywhere.   I need several
cartons.

Any help would be appreciated.

Corbin

email 
corbing
@ 
the big Internet portal starting with Y and ending with O
.com