How to find legitimate organizations that can help single fathers fight for custody?

I have a friend that is a single dad that has been supporting and caring for his son for many years as the mom took off. She literally was only seeing the little boy only 20 percent of the time if that. She came snd took the little boy and kept him. Because there is no custody order my friend is screwed snd doesnt have tons of momey for an attorney. Please tell can you recommend any non profut organizations that can fight for single responsible dads custody rights. Thanks