I don't know how you'd obtain it by way of a FOIA request. I suppose that if he wants you to find him, he'll find you. Why the need for his address (as opposed to sending a letter to his old address and letting the Post Office forward it)?
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FOIA request will not help you in this instance. Have you considered trying his last place of employment, or the numerous third party services available online with money back guarantees for bad addresses? Another option would be to seek out a family member. Good luck.