Window parts

There are no manufacturers name on the windows or these balances. There is a fiberglass rod (about 27" on front one and 25" on the back one. They have plastic fittings on top and bottom (see photos).

Springs are getting rusty, but ok. The plastic blocks are cracking. There are 3 blocks per balance. The bottom one is connected to the spring, and accepts the window arm (little metal thing that stick out of the side of the window). The middle block connects to the top of the spring, and also connects to the bottom of the string. The fiberglass rod slides through the middle of the block. The top block accepts the tip of the fiberglass rod, and also the top of the string.

I have a total of 11 of these windows. Any sort of replacement balance, or replacement parts would be great.

I am the home owner, but also pretty handy and a fast learner!