The man is reported to have entered the premises in Lumley Road in the town at around 1.30am on October 1 and removed a cash register draw from underneath the serving counter.
It is believed he entered the building while staff were receiving a delivery. He is described as white with a tanned complexion, mid to late 20's, slim to medium build and light coloured hair. He was wearing a dark tracksuit with three white stripes on the shoulder and a white band around the middle.
A staff member gave chase, but was threatened by the suspect.
Anyone who can help email link [email protected] please remember to reference incident 14 of 1 October in the subject box.
Via our non-emergency number 101, quoting incident 14 of 1 October.
Through the independent charity Crimestoppers anonymously on 0800 555 111 or online at crimestoppers-uk.org.