I am interested in contacting a service to assist in obtaining a tourist visa for my 20 year old son

Your son's application for China tourist visa should be handed in Consulate General of China in Chicago. The procedure is simple and you can apply by yourself or by anyone you entrusted. Anyway, if you want to go through a service for that, you'd better search online. And of course you need to pay for their service, usually, very expensive. This site is only a platform for discussion about China travel and related China visa issue. I am not sure it is reliable if you get one recommended by someone here .