I think it could be effective to speak with a counselor at your son's high school, who should have this range of information at hand.
In addition, look for support grpups for parents and families of individuals that suffer from ADHD and Autism Spectrum Disorders. These are often listed weekly in local newspapers and many meet in local churches and libraries. These groups would have information that could help you and your son.
Another option is to call the county jobs-services entity, which may be call Jobs and Family Services (state name)Works! or similar. They would certainly have this type of information. The County Board of Education would have resources as well.
Also call your family physician and aany thereapists you have for help.
Best of Success to your son!