Accessory uses incidental to and on the same zoning lot as the principal use. Such incidental accessory uses shall include cafeterias, restaurants, gift shops, flower shops, snack bars, drug stores, barber shops, beauty parlors, banks, and office supply stores (not including office machinery and furniture), conducted for the convenience of the employees, patients, patrons or visitors. Said uses shall be designed and located totally within the confines of the principal use. Primary access to the incidental retail uses shall be from within the principal use. All exterior signs related to said uses shall conform to the applicable sign regulations.