you should be able to get an axel long enough from your local bike shop. There are some issues to be concerned about. Assuming the rear wheel is not sealed, it should be as easy as changing the axel. Make shure your new axel is the same thread as you current one so you don't need to buy new bolts and cones. If the hub is sealed I would take it to your LBS and have them swap it out, it could be more complicated.