Need help in identifying and replacing "friction shoe" or "balance support shoe"

My home has many wooden double hung windows. The manufacturer is unknown (there are no markings that can be found on the sashes or liners). The balance mechanisms are failing because the plastic piece that supports the sash and attaches the cord to the balance spring are breaking at the tab that holds the cord (pictures of an unbroken part included). I believe the windows were installed in the 1980's, but I am not certain of the year. Any help or suggestions to identify and replace these parts will be greatly appreciated.

Tom, thank you for the suggestion. I had noticed part 15-104 during my search prior to posting this e-mail. It seems to have the same dimensions, though it is slightly different along one side (perhaps this is a "friction" plate). I will order some of them, and give it a try. Hopefully they will work. Thanks again for your suggestion,
Jeff

Tom, I used the 15-104 Caradco Friction Shoe, and they worked fine as a replacement for the original part. I had to remove the metal strip which added tension to get them to fit the channel, and after that the Caradco part fit easily into the sash liner, and seems to be working fine. I am going to order another batch of these parts just to make sure I have a future supply on hand should any of the other windows need a similar repair.

Thank you so much for your help and guidance with this perplexing problem.
Jeff

Jeff,
I know it's been quite some time but wondered how the units were holding up and if you have any suggestions or tips? I have the exact same windows with the exact same problem.