Legal Aide provides good service.
As to the restraining order, it has to be served on the mother and then it has to be on file with the courts in order to be enforced by the police. Just having it signed doesn't do it. do you know if she signed it and he filed it?
Has your brother been given total custody by the court?
If all of that has been done I think the next step is to return to court and get warrant so that the AZ police can pick him up. The court might also issue a warrant for her arrest for kitnap if your brother had been given legal custody.
All of this is complicated in that you have to follow all the steps. A lawyer can be helpful but you can do it yourself if you've followed the steps from the beginning. I'd advise consulting with a lawyer to see what he recommends. The first appointment is always without charge.
You might be able to get the names of a few lawyers that have appeared in court from the court clerks who might give you an idea of how they work. This does mean being respectful in a way that is appealing to them. Go when they are not busy. Start with the clerks where you filed for the restraining order.
Once a child is taken out of state it is difficult to get the child back. Each jurisdiction is different. You could call the jurisdiction in which the mother lives and find out from them what you need to get your child returned.
Good luck.