They are hard to find and when they do, they sell them. I suspect some are old stock "after market" parts but hey, if it might work, why not?
As far as that main spring in the Navy (above) it looks like it may contact the T.G material at full **** (somewhere along the belly of the spring). I would remove any of the brass t.g. that does make contact.
You can take material off of the sides of the spring to lighten it some. In the future, if it breaks, it may be easier to get a current Pietta or Uberti spring to use. Get a brass screw the same as the main spring screw or a brass rod to fill in the drilled out main spring screw hole and solder it in place. Drill and tap a new hole for a new screw in the correct position that will allow you to use new Pietta / Uberti spring.
Mike