All purchases made by any agency of the state, whether or not through the purchasing division of the department of general services, or by any county, municipality, or other governing subdivision of the state, or by any public institution, shall be made from an agency of the state or a nonprofit workshop for the blind in Tennessee, operating under the approval of the department of human services and the division of services for the blind. This requirement shall not apply if these products are not available within the time period provided in § 71-4-205, or in any case where products or services are available for procurement from any agency of this state and procurement from any agency of this state is required under any provisions of any law in effect on July 1, 1977.