I don't think you'll have an issue finding a good GSD in rescue. Depending on where you live it may take a while or you might find one in know time at all. I think if you work with this breed rescue and really get a feel for the individual dogs that come through and the breed as a whole you will be fine. Plenty of good dogs end up in rescue for human related reasons: moving, new baby, death in family, etc.
My shepherdy mutt is a great dog