VZ Grips are now making grips for S&W 'N-frames' square butt revolvers.
https://vzgrips.com/gun-grips/smith-wesson/n-frame/square-bottoms (https://vzgrips.com/gun-grips/smith-wesson/n-frame/square-bottoms)
They make some nice grips, I have some on one of my my 1911s and a set on my Rohrbaugh.