"I've been in tears for the past two days because I'm so overwhelmed," Alex's mum, Nat Sutton, said.
"I can't believe the amount of support we have received, a kind lady from the community set up an account for Alex for donations, towards a new bike or to get the current one fixed.
"Another lady tracked me down and offered to pay for a new bike. I respectfully declined, but when she insisted, I offered her the bank account number to make a small donation.
"Then she messaged and said she had deposited the full amount of $480."
Mrs Sutton, a mother of five, said she was not used to people being so charitable, even though the family was "in no way well off".
"We a single income, but we are blessed. I was reminded after turning down [money from] a few people that it was not about me, it was about helping someone who deserved it, who happened to be my son. We, after all, wouldn't hesitate to help someone else in need.
She said Alex was slowly recovering from the ordeal, though he was a bit frightened of going out, and has asked a friend to do his paper run with him.
"He's been caring for a cat while the owners are away for the past three weeks and although it's only been a three minute walk away, he's asked me to go with him.
She said donations -- a total of $630 -- had gone above and beyond the value of the bike, and the account had now been closed.
She said the family had thought about using the rest of the money to "pay it forward" to another unfortunate kid, and would perhaps put some towards a self defence course for Alex, to help him get his confidence back.
A police spokeswoman said inquiries into the attack were continuing.