I have an Old Sterling Mountain Bike. It has a fixed front fork. I want to put on a front shock fork so I can give it to my son to ride. The bike has some good components on it so I thought it would be a good bike for him since he is moving up from a 24" bike. It has the old style quill stem though, which has made it hard to find a replacement fork. Any ideas? It may be cost prohibitive to change out too.