Officers have released an image of the man described as having dark skin, a black beard and long hair which has been tied back.
On the 7th of November the victim took the 170 bus at Victoria Street at 04:37am and saw him exposing himself with his phone in hand.
Another incident reports he exposed himself of the 31 bus in Camden, then used his foot to block the victim from leaving the bus.
Anyone with information on his whereabouts should contact police on 101.