Hire a P.I.

Go to homeless shelters in the areas you know he was last at, and see if you can find some clues from there (take a photo of him when you go there so you can show the people).

That’s terrible, I wish you luck in finding him. If you can estimate the area he’s in and places he may go, I would put up posters around there. Sometimes in these cases there isn’t any organizations to help you. If you could find the most recent pic of him (you said he was arrested so they must have one) I would post it with his information. Hopefully he will see it if anyone. If you haven’t filed a police report yet I would go ahead and do that, it may not help, but you never know. The best thing you can do is take every chance there is to find him, even if it’s just little things like an ad in the newspaper and talking to a lot of people, you never know what will catch people’s eyes and things do spread quickly.