Window balance springs with "omega" clips

I have old wood windows. The balance springs are shot... generally the ends of the springs have broken allowing the spring to retract up into the channels and no longer provide support for the window. In the first photo, you can see a functioning spring that I have pulled down for viewing. A clip, in the shape of an "omega" connects the spring to the bottom of the window. Picture 2 shows the hole in the bottom of the sash where the clip catches the window in a functioning window (this one is already missing). Picture 3 is the bottom side channel. Aluminum. The last picture is of the upper side channel. In it, the rounded area in the center is what covers the balance spring in the top half of the window. I have a carpenter who is available to repair these windows, but will need replacement parts. Do you have or can you tell me where to get replacement springs and clips?