Replacement parts
Looks like you have the old Simonton brand coil balance assembly. They no longer made this, but we have two possible solutions for you to consider.
The first is our 15-192 pivot shoe, along with our Series 170 coil spring (and other parts related to its store page). This is a Certainteed brand part but I have had customers in the past tell me that they got it to work after grinding down the front of the face, which sticks out just a little too far for this window.
The other option is a more modern replacement that I think works just as well, if not better, since it's not prone to breaking in half like your old one is. The video below will go into more detail. This will explain exactly what parts you need to buy and how you can install them in your window. Just note that you will need the exact weight of your sash on hand in order to calculate the proper spring strength. You want to divide that weight by how many springs support the sash, then pick accordingly.
The 15-192 pivot shoe is designed to work with our 26-175 pivot bar set, but please note that these pivot bars are strictly designed to work on Certainteed brand windows only. While the Certainteed shoe can work on the Simonton window with alterations, the same cannot be said of the pivot bars. There are no alterations you can make to those to get them to work.
In some cases the original Simonton pivot bars will work as-is, but you may ultimately need to reuse your original center cam if that's not possible.
I'm very sorry for misunderstanding your original request. I must have been too focused on your photos and overlooked that part. Sorry about that!
Looking more closely at the corroded remains of the original pivot bar, I would recommend the 26-040. You may want to compare this to an undamaged version of the original but the shape does look about the same. Note that it's 5/16" x 3/16" and has a "U" shape.