If you're still looking for The Art of Monsters Inc and don't mind the text in Japanese, Amazon Japan has it in stock. Only limited copies are available. The price is around US$40 not including shipping. For your information, the market rate for the out-of-print English edition is over US$100.

There's a link somewhere on the Amazon page to translate it to English, after that checkout will be in English as well. If you're already an Amazon customer, your account information will be filled automatically. Here are amazon.co.jp shipping rates for your reference.

And here's the book review for the English edition.