Ross Monaghan was shot in the back by a man pushing a buggy near St George's Primary School, Penilee, on 16 January.
The shooting happened as Mr Monaghan, 35, was dropping off a child at the school. He was released from hospital later the same day.
The reward for any information leading to a conviction is being offered by the Crimestoppers charity.
Crimestoppers said the gunman was wearing a blue padded jacket, blue jeans, a woollen scarf pulled up to cover his face and a dark woollen bobble hat.
The attack took place just after 09:00.
Angela Parker, national manager of Crimestoppers in Scotland, said: "It's shocking to think that this attempted murder happened right in front of a busy primary school in broad daylight at the start of the school day.
"The parents of the schoolchildren and the nearby Penilee estate have a right to feel safe, especially when they are dropping of children in front of the school gates.
"We are now offering a substantial reward for information given to Crimestoppers and urge local people or anyone who is in the know to please pick up the phone or log on to our website and pass on information in compete anonymity."
Police Scotland said last week that Mr Monaghan had left Scotland and gone to Spain shortly after the attack on Muirdykes Road.
Mr Monghan was cleared of killing gangland figure Kevin "Gerbil" Carroll in 2012 after a judge ruled there was no case to answer due to insufficient evidence.
A reward of £5,000 is being offered over the attempted murder of a man outside a Glasgow primary school.