Scotland Yard said the man they want to speak to has since “significantly altered his appearance” from the CCTV footage.
People have been urged not to approach him.
A 23-year-old man was arrested on Monday on suspicion of conspiracy to commit murder and remains in police custody.
Ch Insp Allam Bhangoo said: “We remain committed to securing justice for Erdem as our thoughts remain with his loved ones at this unimaginably hard time.
“While I am pleased my team have made an arrest, our work continues at pace to investigate the full circumstances around Erdem’s murder.
“We are now releasing the details and images of a man we urgently need to speak to in connection with the incident.
“We are carrying out a number of inquiries to trace him but are also asking for the public’s help.
“If you recognise him or have any information on his whereabouts please come forward.
“We are still appealing for anyone with wider information about the shooting, including any CCTV, doorbell, dashcam or mobile phone footage, to also contact us.”
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