The Merchant in Hot Springs is the first one who will sell you weapons. Increase this encampment's trust level to at least LV2 to gain access to a better set of weapons, including a shotgun sidearm, a sniper rile , submachine Guns, etc.
Noticeable improvement over the 9mm. More ammo capacity and better accuracy.
Lil’ Stubby
TLV2: 2000
Small unique shotgun that fits in a hip holster. It’s low accuracy and rate of fire is off set by its high damage and the stopping power of a shotgun as a sidearm.
SMP9
TLV3: 1250
Automatic sidearm great for one-on-one encounters but you have to make sure to make each shot count.