Broken plastic parts

That plastic part looks like a component of your rod balance. I'm afraid I have some bad news for you: not only is this plastic component not sold separately (or even possible to replace and still have the balance work correctly), but rod type balances are a very old style that aren't even made anymore. We can still help, but you need to replace the entire balance system with something more modern.

If that interests you, then I will need you to remove an undamaged version of your balance and remove it from the window entirely. Then, I would like a clear picture of the top end, bottom end, and whatever clip or hook is at the end of the cord.

It is very important that the balance you show us is undamaged. If any pieces are broken off or missing then we won't be able to help. These are pretty specific systems and we can't overlook anything.

Please let me know if that will be possible.