Council may establish a Purchasing Agency either as an independent office or as a division of one of the departments created by this Charter, which shall have the duty to contract for, purchase, store, and distribute all supplies, printing, materials and equipment required by any agency of the City, within the appropriations made by Council pursuant to this Charter. Council may designate a Purchasing Agent and provide by ordinance the procedure for the making of emergency purchases by officers and employees of the City other than the Purchasing Agent.