Was wondering what your preference would be for a set of finger groove grips for a J frame square butt? Mainly manufacturer, I've got my own material (wood) preference.
I have small hands with longish fingers, and bought a set of these Craig Spegel grips a few years ago. My pinky still hangs off the bottom, but that doesn't bother me, I've had others I shot just fine that way.
I'm betting you'll find (as I did) that there aren't nearly as many options for square butt J frames as there are for round butts!
I picked up a model 34 and the grip is just way too small for my huge hands so I was just looking for something a bit bigger to make it more comfortable to shoot.
S&W used to make this grip, in both smooth and checkered versions, for J square butts (they also work with round butts, a factory conversion grip):
If finger grooves are a must, as papajohn showed, Spegel is an option. You can also find old Mustang grips with finger grooves for square J-frames. One of the hardest to find is a J square combat grip S&W sold for only a few years in the '80s.
Keeping your eye on the classifieds forum here (and you should place a "Want to Buy" ad there) and the auction sites is the name of the game when it comes to finding these.
I should mention that a grip adapter added to the magna stocks will also help fill in the grip if you don't have any luck finding a larger wood grip.
I have a S&W 36 dating back to the late 60's, obviously square butt. I put Pachmayr Grippers on them many years ago, work fine for me. I believe they still make these grips in both square and round butt.
I have a model 31 that is a square butt. My first try was a Pachmayr Compac style grip (item SJ-CS according to the packaging). I liked it a lot but my wife didn't and it's technically her gun. So I put the original grips back on and added a Tyler T-grip. Now it feels pretty much like her model 34 (round butt) that has a T-grip on it and she's happy. And I like the T-grips too so we're set.