I can see a shadow of the mainspring where it fits against the bolster. That should get you pretty close to the over all size and shape of the spring. If you can't find one from a vendor you could easily make one. (make two) If you decide to make one, it is largely a filing job with one sharp bend. Bend the spring with only a moderate red heat and take your time. Three or four heats should close it up nicely. Many springs break, not because of hardening flaws, but because they were over heated with a small acetelyne flame.