Fresh market in Cary has them. They are expensive at close to $5 per pound, but they have great flavor. They were the best tomatoes I've had since last summer.
Another good place to look for non commercial varieties is the Raleigh Farmer's Market. Several of the vendors have German Johnson tomatoes in the back of their stands. Look for them or ask each vendor if they have them. Remember, ugly is good when it comes to tomatoes.