I understand exactly what you are asking for. Online support is great but sometimes being able to sit in with others who have this disorder and talk in real time, face to face is very beneficial.
I did some searching and did not find any national society for GERD listed but you may want to try Digetive Disorders and search.
Also I would ask your local GI physician as I know ours heads up a Crohns support group so yours may know of any local groups that meet to talk about GERD.
I know this is not much help but perhaps others will have a good idea.