Dave, that is quite the drawbar after looking at Lionel's parts. It broke in a tough spot to repair. The hole where the wire passes through. Not a lot of meat to work with. I've used a splice plate to shorten drawbars. Used a brass strip with 4 holes tapped in it.
The second photo shows the brass strip. I covered it in JB Weld which was probably overkill. The problem with yours is your dealing with a spot the wire passes through and there really isn't much to work with. Where your drawbar straightens out is probably the best place to make a splice.
I went to Lionel's parts site. As you stated the part is unavaiable. What makes their site great is the fact that they have pictures. Below is your S1.
This one is from a T1. Looks similar and may work. If your attempt at repair is a no go. It might be easier to search their site and try to come up with something that may work or can be tweaked to work. You may have to splice it together. But it can be done on the long straight portion where you have something to work with.