The executive director may purchase such merchandise for resale and such operating supplies and materials as may be necessary for the operation of the department. Items for resale may be purchased in accordance with N.H. Rev. Stat. § 21-I:18, I(k). All operating supplies and materials shall be purchased through the department of administrative services, division of procurement and support services. Such purchases shall be a charge upon the revolving fund established in N.H. Rev. Stat. § 206:22-a.