Many programs that are set up for older kids will allow your child to participate if you approach them the right way. I have found that coming across as someone in desperate need of help works for many.
My DS has gone to workshops, seminars etc that were meant for much older kids. I've always explained the situation in advance,asked permission and swore that if my son became disruptive in any way we would leave. The first couple took a major job of convincing, but now many of the people know him and readily allow him in. I also have collected names from people that have hoste events and asked that I might use them for a reference when I run across someone who is hesitant to allow my son to participate.
As far as the group goes, I think I would ask if the school would be willing to pass out a flyer to the GT classes at several schools in the area.
