At 12pm on Saturday (April 30), the woman was working in a William Hill branch on Market Place in the town centre when a man entered the shop.
The man is then reported to have followed the woman outside before spitting in her face and swearing at her. This is said to be an unprovoked attack and the woman was left shaken afterwards.
The police have now issued a picture of a man who they believe was involved in the incident and have appealed to the public for help in assisting them in their investigation.
In a statement, the force said: “Do you recognise this man? We hope he can assist our investigation.”
Those who have any information can call South Yorkshire Police on 101 and quote investigation number 14/81230/22 or alternatively contact Crimestoppers anonymously.