Out of curiosity, Ruger will not sell parts of this kind? Why not?
Liability.
Billy Bob picks up a hammer and installs it improperly. There's an "accident" and Ruger gets sued.
Makes no difference Ruger didn't install it, it's Ruger's gun so obviously they're at fault, according to the lawyers.
For that reason, Ruger, like many gun companies restrict critical parts to factory installation only.
If you send a gun in to Ruger, they will install a new hammer, BUT..... they KEEP the old hammer. Again, liability.