I would suggest picking up a generic choke cable from a parts house. they are pretty long. If you have the old assembly, pull the wire all the way out. The wire is usually soldered in the rod. Heat the rod and remove the old wire. Cut the choke wire to the length you need and solder it back into the rod. The spring cover is usually just a press fit on the tube. work the spring out and replace with the spring from the choke cable, cut to the length you need, and squeeze the tube back together. If the tube will not hold onto the spring, solder the two together. run a long drill down the tube to clear any solder that leaks through. Re-insert the wire into the tube/spring and bend the end of the wire to the desired shape.