North Shore CIB Detective Sergeant Steve Pivac said the female employee was shaken but uninjured.
"The offender wore quite a distinctive jacket that we're hoping someone will recognise. It was a blue stadium style jacket, with white sleeves.
"This was worn over a grey hoodie and a black cap. He was aged in his 20s or 30s and has been described as a fair-skinned Maori, or tanned caucasian with facial stubble, tall (about 170cms) with a medium build," Mr Pivac said.
Anyone with relevant information is asked to contact North Shore Police on 09 213 7898 or they can provide information anonymously through Crimestoppers on 0800 555 111.