Ted,
You might give October Country a try. At one time, maybe 8 or 10 years ago, I believe there were about half a dozen in stock. Whether or not the new owner has trashcanned them or not, I do not know.
In order to replace that spring, one has to unsolder the charger, replace the spring, then resolder it back together. Much easier to just replace the whole charger assembly.
I did talk with Mr. Pedersoli about the poor quality of the spring and the breakage problem but received no real reply that I can recall.
Seems like Richard Beauchamp is Pedersoli's main importer, or at least he was. You could also check with him. He used to advertise in the classified section of the NMLRA magazine.
Hope that info is of some assistance.
John