You probably already know about this site but in case you don't... The Unofficial P-64 Resource
The moderator (normsutton) on there is a gunsmith and offers springs and small parts should you need anything.
Best of luck with your new pistol.
BTW: Don't listen to all the recoil sensitive wussies that say you have to change the springs. My P-64 shoots great and is bone stock. Shoot it before you decide to make any changes.