There are a many many resources to find used boats in general and specifically a Seafarer. GW and Plymouth are right, it may take a little effort to find the “right” one, but they are out there and or will come onto the market. What will be key for you, is to recognize what represents a good listing when it becomes available and be ready to react.
Presuming you’re in MD, I’d continue to check The Hull Truth, Tidalfish, UsedBoats.com, The Capital, The Easton newspaper, Craig’s List, EBay, other used boat web sites, the GW dealer in Deale & DE and this site. I also wouldn’t be averse to traveling within the mid-Atlantic to go get one if an initial investigation looked promising. If you want one, and the owner wants his listing to be found, you can find them.