I have attempted to attach photographs of the spring unit which I have removed from the window. These windows were installed in our home in 1988. I had previously purchased some replacement springs directly from the manufacture, but they no longer stock them. They advise that I could go online and locate them I believe That if I can get the right one from you, everything will be fine.
The metal portion of the spring unit measures 22 inches and the width of the channel brace is 1/2 inch.