Surviving flying boats are a rare thing. The problems with airframe life become massively multiplied when you factor in highly corrosive seawater! I do remember seeing a PBY Catalina at (I think) the Flying Legends show at Duxford a couple of years ago. They were trying to raise funds to restore it. It actually looked in pretty good shape. About the closest you'll find to a flying Sunderland would be the massive Martin 'Mars' flying boats which if I recall correctly are used for fishery and fire fighting operations in North America. An impressive bird if ever there was one, check it out at:
http://www.martinmars.com/