The theft happened some time between 11am and 11.10am on Tuesday, January 24 when the victim was making her way out of the store.
She was putting her cards back in her purse and then back in her handbag, but before she could close the zip, a man approached her and placed his hand in the bag and took one of the cards out of her purse.
He is described as white, aged about 40, with blonde hair. He had a slim build and was wearing a dark padded hooded jacket jeans and trainers.
Witnesses or anyone with information about this incident can contact police on 101 or Crimestoppers anonymously on 0800 111 555.