Try Legacy Cargidans in Greer SC. Not really close to Northern VA, but she will find a way to deliver if you need it. We've got 3 from Sharon, one a merle. They're great. The merle (Ragnar) is a little crazy, but sweet, and the other two are the nicest tempered dogs you'd want to know. Ragnar and Kelso are half brothers to the featured dog on her home page, Cain.
You could try contacting Joanna at blacksheep cardigans. She's not really very close to you but she's on the east coast and might have more info. When I started contacting breeders several of them took over a month to respond.
Maybe you saw this already, but Joanna has an older puppy from their last litter available on her blog. I know you said you wanted a merle, but he is a really gorgeous flashy black and white boy.