I went looking for some of the parts you mentioned and found the trigger group
here. It's labeled only for the 9x21 IMI and .40S&W so I'm unsure if it would work with the 9x19 we all use here or if they didn't bother to label it as such since they can't sell stuff for military calibers in Italy.
This is mostly for others since you probably already know this, but
here is the section with all the special PX4 parts. Sounds like they use a low friction coating called DLC (Diamond Like Coating) that supposedly does stuff similar to NP3.
The locking block they sell is especially labeled with the DLC coating. The neatest part I see there is the 90 series style safety levers for the PX4 (
Beretta Leve Sicura Tipo "F" R.P.) as I don't really like the style the PX4 comes with.
I wonder if I could get these parts shipped to the US...