It is reported that a man approached the victim in the station on July 16 just after midnight.
British Transport Police (BTP) officers have since been investigating the incident.
An image has now been released of a man who police believe may have information.
Anyone who recognises him is asked to contact BTP by texting 61016 or by calling 0800 40 50 40, quoting reference 131 of 18 July.
Alternatively, contact Crimestoppers anonymously on 0800 555 111.
