The company that is listed in the related links IS NOT the Buffalo Arms in question that made Buffalo Arms Derringers. The company went out of business long ago, and there are no known websites, or information regarding them.
The Buffalo Arms Model 1 Derringer operates using a simple single-action mechanism. When the hammer is cocked manually, pulling the trigger releases the hammer, striking the firing pin to ignite the cartridge primer. This compact firearm typically features two barrels and is designed for easy concealment. It is loaded by breaking open the action to access the chambers for insertion of cartridges.
50
This would be a Davis Arms .22 Caliber Derringer.
100-300 USD
Numrich Arms has a great supply of parts for the Glenfield Model 10.
Numrich Arms.
Fairly obscure 22 derringer, made in Germany by World Arms. Value in the $50 range.
Google Numrich Arms. They have many parts.
the arms
the arms
Numrich Arms is a good source for gun parts.
You will need tihe services of a good gunsmith