One hundred bucks cash right now!
You sure you can't just train past it? I find my GP real easy to stage the trigger. Perhaps a spring package...
from time to time Numrich Gun Parts Corporation has a parts kit for Ruger GP series with the entire hammer, trigger, ratchet and cylinder stop included. A competent smith should be able to drop it in and get you up.
My son, you will travel far, but never be alone, for I am with you, my M14 and battle axe comfort you.