But they believe as many as 15 witnesses who were there in the early hours of Saturday, November 18, have still not come forward.
Detective Chief Inspector Scott Wilson said: "We want to speak to these people even if it is just a matter of eliminating them from our enquiries."
It is believed a row broke out in the club between Mr Arthur's friends and another group of men.
Punches were thrown and someone drew a gun and shot Mr Arthur in the stomach at around 5.30am before fleeing the scene.
Mr Arthur was taken to the Royal London Hospital in Whitechapel and pronounced dead on arrival.
Detectives are waiting for forensic tests which could provide important evidence in their attempt to find Mr Arthur's killer.
Last week they revisited the club to try to jog people's memories.
Officers parked a mobile police unit outside the club on Friday night and quizzed passers-by.
Anyone with information should call the Trident incident room on 020 8733 4704 or Crimestoppers anonymously on 0800 555111.
* A man was arrested on Sunday in connection with Mr Arthur's murder. He was bailed to return to an east London police station in two weeks.