This is a source on building a Custom P365XL. I have found some of the best deals for you all!
It all starts with a Fire Control Unit (FCU) or a Complete Firearm. The FCU is a serialized "Firearm" and will need to be sent to an FFL
Fire Control Units and Complete Guns
Frames / Grip Modules
These are NOT regulated and can be shipped to you directly.
Faxon P365 XL Straight Fluted Barrel, Threaded, TiN PVD
Faxon P365 XL Straight Fluted Barrel, Threaded, Chameleon PVD
Faxon P365 Straight Fluted Barrel, Threaded, Nitride
True Precision P365 Threaded Barrel
Zev P365 Barrel