Well, since YOU mentioned children's books, here are some auctions currently on ebay:
Spanish:
http://shop.ebay.com/i.html?_nkw=chi....c0.m270.l1313
Japanese:
http://books.shop.ebay.com/Children-...=p3286.c0.m282
Just watch the S&H to make sure it's Media Mail. It can get pricey but worth it.
Last year, I helped my mother's aide buy a lot of books for her children on ebay- the condition of the books varied but all were readable. Hey, kids used them. But she ended up with, like, 70 Dr. Seuss books for under $30. Can't beat that. And her kids LOVED their little personal library.
I have to say, the thought of you adding Arabic to your repertoire made me laugh. Then you'd be reading left to right, right to left and top to bottom. :wink: I get a headache just thinking about it.
Good luck with your studies.