Downhill bike

Hi all I'm looking to fundraise for a local boy who loves downhill biking and would love to get into the sport. At the moment he only has a Argos cross bike but his dream is to have a full down hill bike his mum would appreciate it a lot if anyone can help to raise the funds to buy him a second hand bike. He has autism and trying to find activities to keep him entertained is stressful on her but he loves bikes and learning how to maintain them so please help as much as you can many thanks