Alex is believed to have fallen from the Tyne Bridge in the early hours of Tuesday morning.
The ChronicleLive reported that Alex's family and friends have urged the public to participate in Saturday's search as they desperately try to find him.
Alex's sister Ashleigh Marr said: "I will be at the river everyday looking for him until we find him.
"Please could I ask anyone, people who knew Alex and people who didn’t to come together and help us in this search.
"If anyone has any spare time or is in the area – even for just half-an hour.
"Don't look towards the buildings on your walk - look towards the water."
Ashleigh said her brother was wearing a green parka jacket, grey joggers and blue Nike trainers when he vanished.
"The river is dark, cold and dirty," she said. "Please help us get our Alex out of there. He shouldn’t be in there."
Northumbria Police confirmed that they received a report of a concern for welfare for a man on the Tyne Bridge at 2.15am on Tuesday.