There's nothing you can carry that definitively states that OC is legal in NC. That's because laws do not tell us what we can do- only what we cannot. They also set legal restrictions on activities that may be legal, but are limited in scope based on location, age, and other conditions. Anything not specified by law as illegal is legal. Hence, since there is no law outlawing the practice of openly carrying your handgun. It's legal, although with certain restrictions.
Ask him to show you the exact general statute covering the crime of "Openly Carrying A Handgun". He can't, because there is none. What he can find, however, are laws that describe where the practice is unlawful or restricted. These are very specific in nature for the most part with the exception of the biggie called Going Armed To The Terror Of The Public. To be charged and/ or convicted of this one, though, would require the state to show that you had the intention of causing terror while carrying (basically). It's already been ruled that simply carrying a holstered handgun in public is not sufficient to be convicted of GATTTOTP. They have to prove that your intent was to terrorize others by doing it. Good luck with that one, Mr Sheriff.
Some might say that by you simply carrying it, it's enough to cause terror in people. Meh...
You could carry around every law that deals with the open carry of handguns, or you could go to the NC Attorney General's website and download the latest version of their .pdf file that deals with handgun laws. The NC AG's office will not give you legal advice, mostly because they do not work for you, they work for the state. The state of NC is their client, not it's citizens. But, the file is immensely helpful when trying to figure out some of these laws. It's basically a "Do's & Don'ts" of carrying in NC.
In short, the sheriff is an idiot. He's either uninformed of the laws involved, or he's intentionally misrepresenting them. Either one shows a distinct lack of professionalism and character within the scope of his office. He's paid by that county's citizens to be better than that. Within the scope of the subject of OC, he's woefully inept and probably intentionally causing undue legal ramifications for the residents of that county.
Personally, I wouldn't waste my time trying to educate the entire sheriff's department in your area. It's up to them to know the laws, as well as enforce them in a manner that's legal and professional. If they can't handle that much, then perhaps it's time to look for a new sheriff when election time comes around in your area.
Open carry is legal in NC. There are restrictions, but it's not illegal, no matter how he wants to interpret the laws.