andersen window sash spring balancer

I need replacement window sash spring balancers for two of my Andersen windows that date to 1977. They are double hung windows and the exposed glass area is about 24 1/8" by 32 3/8" for each top and bottom window. Overall window dimensions are 36" by 54". The number 77/0 is stenciled on the lower left portion of one window and 77/1 on the other window.

I found the following number stamped on one of the balancers: E41 9#27 9-77
The dimensions of the balancer are about 6 1/4" by 3" by 3/4".

What replacement part do you suggest?

Thanks