Lawson Marriner Escort
Try going to the central plaza (Lion Court) at exactly 40 minutes after the hour (7:40 pm, for example). From what I have noticed this escort and the moa racers escort seems to happen only once per cycle at this specific time.
Marriner comes out of one of the destroyed houses on the northwest side of the central area and I think the moas come from south of the Priory entrance waypoint.