I would highly recommend Noriko's.  Their cel
books are very high quality and are rather 
inexpensive too.  I bought a 14" x 17" cel
book from there a while back and it's kept my
collection all nice and cozy.  I recently ordered
some bags and a book for my pencil boards too.
They are all professional quality and acid-free
which is, of course, very important.  The 
response and shipping time for me has 
always been very good too.

Faris Kalin, bard extraordinare