At this point in time, to the best of my knowledge, there's only one brass grip frame being currently produced. Ron Powers makes a two piece "Colt Like" grip frame in brass that will fit the Ruger Single Actions.
Over the years the aftermarket industry has made lots of grip frames for the Ruger, however, they are drying up. Ruger made brass Super Blackhawk grip frames in the '60's/early '70's but they are getting difficult to find and become rather expensive due to we collectors.
QPR made a smaller, XR3-RED version for quite a few years and one can occasionally be found at a gun show, etc.
This pair of Old Model Blackhawks are "owner fitted" with the QPR grip frames.
So, I guess the bottom line is that the brass grip frames are getting scarce unless one wants the "small" sized design.
JMHO,
flatgate