All of the new parts from Smith & Wesson and Brownell's are MIM parts.
Keep your eyes on Gun Broker, because when forged pieces come up for auction, they move quickly. If You're looking for the target hammer/trigger, You may find them in color cased, but stainless pieces are becoming very scarce.
Make sure that You buy a K-Frame hammer for rim-fire only, as hammers are unique to each frame size, and rim fire hammers are different than center fire.
Triggers will interchange between K, L, N frames.