Milgard Window Sash
Hey there! We do not carry this exact coil balance assembly, but we should still be able to assist with a replacement. Take a look at the 15-177 pivot shoe. These function a bit differently than your old springs, because the spring screws to the shoe instead of hooking onto it, but it should still work fine as a replacement.
This pivot shoe is compatible with the Series 152 coil springs. To figure out the spring strength you need for your sash, you'll check the old spring for a stamped number that you can match.
If there are no stamps, or you are not able to cross-reference them, you'll need to obtain the exact weight of the window and divide it by the total number of coils in the window.
I've also linked a few other pieces of compatible pieces of hardware. Let me know if you have any questions.