The store in Beith, North Ayrshire, was targeted on February 19.
A man with a weapon entered William Hill on Eglinton Street at around 9pm and demanded cash from staff before making off with a three-figure sum.
Police Scotland have released a picture of a man wearing a black motorcycle helmet who they say may be able to assist with their inquiries.
He also wore a black motorcycle jacket, dark trousers and white trainers and was carrying a dark-coloured backpack.
Anyone with information is asked to contact police on 101 or Crimestoppers on 0800 555 111.