Ace Hardware still sells individual craftsman tools and has a good selection, though I don't think they carry individual sockets.
When Lowes bought the Craftsman brand, it created a big legal mess. Sears sold the brand but was still trying to sell the tools. Sears is basically a dead company living on the fumes of its decaying corporate corpse. Quite a fall for those of us who can remember the Sears catalog being the ultimate wish list as kids. But Lowes has reinvigorated the Craftsman brand as a competitor to Ryobi.
I read somewhere that the parent company for Craftsman (Stanley?) tried to bring hand tool production back to the US, and built a factory in Texas, but they failed and shuttered it without ever producing a single wrench or socket.
Edit: news story on Craftsman factory in Texas
here