Hey Dan;
I called Island Hideaway Campground in Buxton and their rate for a tent and vehicle is $17 per night, ph 252-995-6628. No hookups, but they have a bathhouse with hot showers, etc, about a mile from the Lighthouse.
Island Hide-A-Way Camping
Also called Cape Woods Campground in Buxton and they said theirs are $26 a night, $33 with hookups. The lady said she'd be there til 8PM tonight, in case you're interested, ph 252-995-5850.
Cape Woods Campground
Those are the only ones I could get on the phone this evening, not sure if either would work for you, a little bit of a drive from Hatteras. Here's a website that lists all of them:
Outer Banks Motels and Campgrounds
Brian