that map shows the locations he appears and it should help you out as it worked for me.
i did it after i finished the main story, you will need to enter / exit a building to get him to appear bear in mind. once you find him again, enter another building and check the locations on the map.
sometimes he is approx 100m away (in game measure). use detective mode and look for a blue guy high on a building, or on top of the ferris wheel. it shouldn't take you long to get it now.