I just went down this road in restoring a Hegar Kickstart. Googling Torsion springs leads you into crazy town trying to spec the right springs, or having to pay big $ to have a run of 100 made by a spring specialty company...haha. Anyway I found these springs on a surplus supply site, and was able to make them work for my situation. The spring metal was malleable enough so that I could take off one "loop" and bend the tabs to fit my housing. The picture shows the broken original spring and the replacement that I modified for my use. This spring may be too large for your use, at around 1.5" center diameter though. If you want one, let me know. PM me your address and I'll send it out to you.
Andy