Replacement Window Balances

I am hoping you may assist me in finding replacement balances for the windows in my house. My home was built in 2000 and has the original windows. Several of the balances have failed and before I am forced to replace the windows (which would involve removing half of the siding on the house due to the integrated J channel) I am hoping I may be able to just replace the failed balances. I have attached photos from one of the balances I was able to remove. The small metal tab was screwed in at the top of the window channel with the bottom of the window sash secured in the black T shaped piece. The only identifying mark that I could find on the existing part was a Patent #5.737.877 I believe this is an older style rod-type balance which isn't used any longer so I am hoping you may have a viable alternative. Any assistance you can provide would be appreciated.

Thank you for the assistance. Based on what you provided I measured and found that the existing balance was 28.5" from top to bottom, had a 1" shoe, and weighed 18 lbs. Based on this I would want to order two (2) each of the S795-28B channel balances, 15-194 shoes, and 26-021 pivot bars per window. I just wanted to verify that this was correct. Thank you