I am from the UK, heres some ideas you might want 
to consider:

(1) Getting them from someone like Drac, & 
getting it posted surface mail.  Surface mail for 
a cel book is not much... i think about $4.  It 
may take a while to get to you but that's the 
tradeoff for surface mail i guess.  But many 
times i have actually received surface mail in 
less than 7 days!!

(2) If you know someone going to Japan on 
holiday, then it goes without saying you MUST 
give them a shopping list (lol).  Ask them to go 
into a 100yen shop & get you some B3 pocket 
files.  I have plenty from when i went to Japan, 
they don't get much cheaper than this!

However they are not professional cel books so 
you may not like this idea.. or any of my ideas 
since i am a cheapskate.. lol

Some Japanese sellers on ebay sell them.

Or u can obtain B3 pocket files from some good 
stationary shops... i managed to find some in the 
UK after some searching.  B3 is bigger than 
standard cel size but i find them better than 
11x14 books as it is easy to get them in & out or 
if they have a bigger background.  Great for many 
oversized cels.  If you have some really 
oversized cels then you might consider getting an 
A3 sized one, those are probably more common.

Again these are not professional cel books.

(3) Try www.AnimeAssylum.com (i think that is the 
url).  They have proper sized cel books for 
cheap.  I think $9.99.  Not that much to ship,  I 
bought some cels with my order & they gave me one 
free!

Hope this helps.

:)