Police are investigating the theft from Bookers Cash and Carry on Glasgow Road in the town. It is believed to have happened at about 4.15 pm on Sunday.
Officers are keen to speak to the occupants of a white Ford Transit van seen nearby at the time.
Constable Gary Bil said: “This theft took place in the middle of the afternoon and I would be keen for anyone who was in the area and seen anything suspicious or the white van to get in touch with police via 101”.