OBNB doesn't sell books, but you may be able to find a copy at one of these websites:
The speech of the birds : concerning migration to the real, the Manṭiqu'ṭ-Ṭair by Farīd al-Dīn ʿAṭṭār. ISBN 0946621705. Published by Islamic Texts Society in 1998. Publication and catalogue information, links to buy online and reader comments.