What sort of people were you thinking you might want to give this card/info to? Don't know of anything official but you could make something yourself. I was recentlly involved in a group that designed an 'Emergency Card' to be carried by children with complex health needs or ASD in our area. It has basic info on it such as parents contact phone no, GP, Paediatrician, primary diagnosis, allergies, "things you need to know about me" & other useful info (eg communication needs, epilepsy etc. -just basis stuff without going into any great detail. This was designed to be used when there is a problem though, but it sounds like you just want something you can hand to people who might be caring for or supervising your DS. Could you produce a small leaflet on your PC which just gives enough info writen in appropriate language for the recipients, which can then be handed out to those who may need to know?
Its a good idea to let people be given one of these cards if the are finding DSs behaviour a problem. I'm a nurse and every now and then a relative would hand me a piece of paper with the description of some obscure genetic condition so we knew what we were dealing with! I didnt take offence just grateful the person had the foresight to do this. Of course it helped the patient too!