I always recommend Eagle Grips for maximum comfort and concealment. The Secret Service line particularly accomplish both goals very well. I have them on my Models 58, 520, 13 4" Square, and 13 3" round. I always order them direct and upgrade to the "select" rosewood and nickel screw and escutcheon. These grips are not cheap, just shy of $300 but so worth it IMO.
Eagle also makes "combat" style and "target" style as well. They are less "fat" than S&W versions of those styles.
Altamont also makes some nice grips at very affordable prices in many different configurations, though there are often complaints about sharp edges on the upper end of the backstrap.