The woman was harassed by the man, who was wearing a high-visibility jacket and trousers, on a Saturday morning in Perton.
He allegedly chased the woman along Gainsborough Drive, a residential road that also contains Perton Middle School, while touching himself at around 7.20am on November 20.
The woman managed to escape and raise the alarm by calling a taxi and is said to have been left very shaken and distressed but unhurt.
Police were called around an hour later and have now released an image of a suspect they want to track down.
The man is described as white, in his mid-30s, around 5ft 8inches tall, with short brown hair, of stocky build, and unshaven and is said to have had a very deep voice.
He is not known to the victim.
Chief Inspector Dave Wain, of South Staffordshire Neighbourhood Policing Team (NPT), said: "We are taking this incident very seriously and we will do everything possible to ensure the perpetrator is located."
Officers have increased patrols in the area and are appealing for anyone who who saw what happened, or who may have further CCTV or dash-cam footage of the area from the time, to contact Staffordshire Police on Facebook, Twitter, or by calling 101, quoting incident number 162 of November 20.
Alternatively, Crimestoppers can be contacted anonymously on 0800 555 111.