Daryl,....those springs are available from any of the suppliers to the gun trade,...I had some oversize blanks that came from Italy but used them all,...I think it was Salopian that posted the name of a place that supplies the gun trade in England.
Getting the spring will be half the battle,..fitting and properly timing them is not an easy job. I have some blanks that I had made but they will need hardening and tempering as well as fitting,... let me know

CJ

The taste of poor quality lingers long after the cheap price is forgotten.........