The man is believed to be driving a silver minivan, possibly a Chrysler Town and Country.
He is described as a white male, approximately 30-40 years old, about 6 feet tall with a medium to heavy build, broad shoulders, light brown or sandy blond wavy hair parted in the middle, and wearing a bright red or orange sweathshirt.
Anyone with information on this man is asked to call Silent Observer at 231-722-7463 or call 911.
Heeringa was reported missing shortly after 11 p.m. Friday from the Exxon Mobil gas station located on Sternberg Road just west of U.S. 31.
The 25-year-old woman was getting ready to close the store for the night. She had been working alone and there were no surveillance cameras installed at the time.
She has not been seen or heard from since that time.
Family, friends and many volunteers have been searching the area and putting up posters everywhere they can since officials determined on Sunday that Heeringa had been abducted.
A candlelight vigil for Heeringa is scheduled for 6 p.m. today at The Pointes shopping plaza, just west of the gas station. Participants are asked to bring candles.
Donations will be accepted for the family's expenses and for a reward fund.