The incident took place at around 14:30 on Friday, at the shop along the Rohais.
Police say the woman was of Asian heritage.
Officers would like to speak with anyone who was in the area at the time and may have seen the man, who was accompanied by another person.
They are also looking to talk to the victim, in confidence.
Anyone with information is asked to contact PC 17 Kusimo on 725111 or call Crimestoppers anonymously on 0800 555 111.