The back action hammer action used in the Bernardellis is similar to the hammerguns made by many Italian workshops in the 50s and 60s. The general supplier to the Italian gun trade, the firm Omps, still supplies parts for these oldies and it is an even bet that the springs are common to most of them.

Look up Omps Italia on the net. The address used to be omps.it, but was reported to have changed recently.