constant force balance

I need to replace this window balance. I can't find a manufacturers mark anywhere on the window. It is a large floor to ceiling window. I would order a replacement spring but I can't figure out how to attach the spring. The footer is 1 1/8". the channel is 1 1/4". The second photo is the part that screws into the channel. I would like to replace them both. Very easy to remove but I am unable to find the part. Thank you.

Just found out these windows were manufactured in the early 2000's by a company in South Florida and sold by Home Depot. Home Depot has not been helpful in finding the part so I am still in the dark.