Walther, Beretta, Browning. Kel-Tech, NAA
MId west gun works.
try egunparts
You can start your search at browning themselves,if you have no luck you may want to go to numrich gun parts corp.
Try Numrich gun parts
Try the Gun Parts Corp Hurley NY http://www.e-gunparts.com/
My best advice is to save your money and buy another firearm. Rohm's were not made to the best of standards and parts are almost non-existent
Contact Browning
Try gun shops, gun shows, Shotgun News, want ads, e-gunparts.com
To turn your tanfoglio gt380 into a double action pistol can take a lot of work. You will have to buy a lot of different parts and a lot of time to make this work.
One can purchase Nomad travel accessories from Nomad Travel's official website. They have plenty of different accessories to choose from and even has free delivery on all orders over 75 lire.
you can find some parts like a new or used bolt assm. or parts matching the carbine from brownnells.com or cheaperthandirt.com but sorry no luck finding a new pistol stock. (if you do buy a bolt for it make sure you buy the right one there's two types, a flat, and a round and you must use the same type)