Oliver North is traveling the country selling bulletproof vests. North, who is chairman of Guardian Technologies International, was mobbed by admirers when he arrived in Greeneville, Tenn., Wednesday to pitch his company's product to police officers from Virginia, Kentucky and Tennessee. North said he helped found Guardian Technologies three years ago after leaving the Marine Corps. The retired lieutenant colonel was convicted in 1989 of aiding and abetting obstruction of Congress, destroying National Security Council documents and accepting an illegal gratuity in connection with the Iran-Contra scandal. One of the convictions was reversed, and the others were set aside for further proceedings.