Eleanor Mair, 46, was last seen at a premises in Reform Street at 6pm on Thursday.
The image shows her in the company of a man who helped her while in the shop and officers want to speak to him.
Inspector Cath Lannen said: “We are keen to speak to the man depicted in the image, he has helped Eleanor whilst she was leaving the premises.
“This witness may have information that can assist the inquiry and I would appeal to anyone who recognises him or Eleanor to get in touch with Police Scotland on 101.”
Ms Mair is described as being 5ft 9ins tall, with shoulder length hair, medium build and was wearing purple-coloured clothing when last seen.
She walks with the aid of a crutch.
The man is described as being around 5ft 9ins, of medium build, with grey hair which is thinning on top.
He was wearing a black jacket at the time.