20-50 USD
I THINK your derringer may be a RECK. Value about $25-$50.
What is the value of a Davis Derringer pistol magnum 2 shot?
Check with a gunsmith. These were inexpensive guns to start, and there are not many sources for parts. Depending on the part, a smith may be able to make one, but the cost may exceed the value of the gun.
50-100 USD
35-90 USD
100-200 USD
20-80 usd
100-200 USD or so
100 USD or so
10-60 usd
Maybe 70 USD
20-50 USD or so