1950 Spiral Balance

I have double hung sashes from around 1950 that use spiral balances similar to what you offer. However, my balances are completely contained in the lower sash. The tube is 1/2" in diameter and has a spiral groove running it's full length. The bottom end has a bracket with a bearing point for the center rod and rotating spiral barrel. At the top is a flat tab that is 2" long and 1/2" wide. It is attached to the window frame with one flat wood screw. Inside the spiral barrel is a spring that provides tensioning to counterbalance the sash; the top tab is attached to a bracket fastened to the top end of the spring. Distance from top bracket to bottom bracket is 25". The sash is 28" x 28". Do you have a spiral balance that would work as a replacement for this unit?