Window balance

We bought our house a few years ago. The window balances keep breaking. Turns out, the windows were done by a shady local outfit that went out of business not long after the house was built. The balances are screwed in at the top through a plastic piece. (That's what keeps breaking),the plastic connects to a spring wrapped around a fiberglass rod (like a tent pole). At the bottom, the spring is connected to another plastic piece which connects to a string that goes to the bottom guide.

The design is horrible. I don't expect to get the same parts, but we do need something that can connect to the bottom window guide as I can't see how to remove it.

Also open to other suggestions.