RW99 window

A home owner from Rhode Island. says:
I think I have sent you a picture of the parts. The balance spring and rod that the window slides up and down on to keep the string taut is broken. When we lift the window up, it falls down. We have to put in a brace. We think one of the white plastic parts may be broken. I can send more pictures if you need them. There is no name on the window. From googling is may be wetherweld riverdale.

Measurements of parts in picture:
25 1/4 inch rod
13 1/2 inch spring
33 inch string
1 inch single white plastic
5/8 inch by 1 1/4 inch white plastic attached to spring
5/8 inch white plastic attached to other end of string. This appears to be a broken piece.
User submitted a photo of a window balance.
Profile picture of Tom
Tom from SWISCO responded:
Take a look at our Series 860 balance, this looks like it could work for you. I note that your old balance installed at the top with a nylon hook, but it's hard to tell. Our Series 860 installs using a screw tab, however. With that in mind, I also recommend our 26-200 screw plug. You can pop this in the hole where the old nylon hook went, which will allow you to then screw in the new style balance. Let me know what you think.
How to install the 26-200 Screw Plug
How to install the 26-200 Screw Plug
VIDEO
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Modifying the Series 795 Balance
Modifying the Series 795 Balance
GUIDE
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