You'd need a court order and that order then needs the court to approve the mental health professional who is doing the assessment. So first you locate the professionals, then you file a motion with the court and request the order be made, and when you go to court you can provide the court with their names and (CV). The fees would vary, depend on the experience and expertise of the professional, likely as well, where you are in the state. Last one I did, in 2011, just under $3,000.