There's one more option, but you've gotta have a little dough, you've gotta be REALLY savvy in the gun show circuit to find one, you've gotta have patience while it's being transformed and, well, you gotta have good gun karma to find yourself in the position of putting it all together.
I dream of one...
Search "Hammer It" and his revolver and his posts about it.
Put
THAT one just above the GP-100 in the list.