Go to a fastener store and try to find a bolt with a non threaded length to suit your need . You can cut to fit your need . Take a hacksaw and remove the "extra" , leaving a couple of threads and spray this with whatever you feel comfortable with .
FWIW , When the shock bolt is tightened , the only thing that is gonna "move" is the rod end on the shock . Yjis bolt and everything it tightens becomes one piece .