You can find a new weapon in Remnant: From the Ashes' DLC Subject 2923. You have to dig a bit and if you don't come across it in your first game, don't worry. As long as you go back and study various places in a particular order, you should be good.
Find the key to the servant's door
The first thing to do is visit the Deepfrost Expanse to locate a dungeon called Watcher's Hollow Dungeon. Go through the entire area to the end. You should see a shiny red object inside a hut called the Servant's Door Key. To the right of the shelter is a shortcut that you can take to return to the start. However, turn right and you should see a locked door. Use the Servant Gate key to open it and find various servant rats all huddled together. Kill the rats until an item called Creeper's Pepper drops. It should go into your inventory. You can then leave the dungeon to continue your journey.
Rat statue
Now you need to venture further into the Deepfrost Expanse until you come across a Rat Statue. The statue must hold a large ax in its left hand, its right holds a stone and has a green eye. The Creeper's Pepper is the missing eye. Interact with the statue to place the eye inside and you unlock a secret passage behind it. We were able to find both the Watcher's Hollow dungeon and the rat statue in our first game, but it might take you a few times to appear on an adventure.
Go behind the statue to venture into the new passage you have discovered. The Twin Shot bow will be on the table at the end of the secret passage. It occupies the slot of your handgun.
