The 89-year-old man was at the cash point outside Sainsbury's on Greenwood Avenue when he was approached by two male youths on bikes.
They grabbed the money from him before riding off . The man, who was on a mobility scooter who is hard of hearing and sight, wasn't hurt during the incident.
The youths have been described as white and in their late teens. One was wearing dark blue clothing and riding a distinctive lime green mountain bike.
The other was wearing a khaki green coat and blue jogging bottoms and riding a silver mountain bike. Police are appealing for witnesses.