single hung constant force coil balances

I need to replace the coil on both sides of a single hung window. Both coils are broken.
Window sash weighs about 13 lbs and is 23.5 inches high. Probably just need coil replacements. Coil is 1/2 inch wide. Looks like Series 175 silver. Shown in the picture are the bottom shoes and the broken parts of the coils on the upper brace.