The theft took place in the car park at Aldi in Tildasley Street, West Bromwich.
It happened as the driver was helping a man with directions – when a second man leaned into the car and stole the money.
It took place at around 10.50am on February 25 and police have now released a CCTV image of a man they wanted to speak to in connection with the incident.
A spokesman for West Midlands Police said: "Do you know who this man is? We want to speak to him after cash was stolen from a car in West Bromwich at around 10.50am on Thursday, February 25.
"As the woman driver was helping a man with directions in the car park at Aldi in Tildasley Street, a second man leaned into the car and stole the money.
"Our investigations continue and if you know who the man in the image is, to contact us."
Anyone with information can call West Midlands Police on 101, quoting incident number 20SW/56412Q/21.
Alternatively, witnesses can call Crimestoppers anonymously on 0800 555111.