The two men entered the Hall and Coates outdoor clothing shop, in Church Street, at around noon on Saturday.
One of the suspects asked to try on a pair of boots and, while the shop assistant was in the store room, a second man stole a number items.
The thief took a series of Sealskinz branded clothing, including gloves, hats and socks, which are valued at between £200 and £300.
He left without paying and the second man followed shortly afterwards.
Anyone with information is asked to call police on 101, quoting incident number 12170166285.