Where did you get it from - can you go back to them to ask advice? The Health Board provide them (major buggies) here, so you could ask yours for a temporary loan, but from wat i gather they're in short supply (like everything else). you can buy them now I believe, on ebay etc. x
Thank you for messages, I phone my local Disability help center, believe it or not all these charities had plenty of available mobility aids for adults but none for children. I found on ebay, but would take 4-7 working days to get to me. Manage to get the repair shop to repair it as a favor urgently. Hopefully will get it by Monday. Bought a foldable wheel chair from Halfords in the meantime.