It IS legal to be topless at Topsail Beach and on Okracoke in the National Seashore.
The National Seashore area has a campground (also legal to be topless THERE!)and it is large enough that if you drive way up the beach, away from the fishermen, then you can be nude as long as you are ready to cover up quickly if needed! (sit on a wrap!)

I am a lifelong North Carolinian and those are the only places I am aware of on our entire coast.