Check out members.tripod.com/NRWILLIAMSON/dialcord.jpg
It gives a stringing diagram for a dial cord to replace the "O" ring.
Also check out a hardware store that specializes in plumbing supplies. You will probably have to ask at the counter as they will not be out in the main store. They may also have a make-it your self kit available. If they do not have it they may know who does.
Also check out www.ultrawebb.com/OHP.