Mikey,
Eagle Grips ("Regular") makes something real close to the smooth S&W Magnas. I haven't handled them so I don't know if they're the same thickness, but aside from the medallion they look about the same.
I just ordered a pair of their "Secret Service" grips for another N-Frame square butt that I'm getting. I expect to thin them down and make the finger grooves a little less obvious, but I'm thinking they should do well for what I like. Ebony, which may contrast nicely with SS, too.
-Don
P.S. Got the Eagle grips and they were already nice and narrow, but there was too much material behind the trigger guard. After removing quite a bit from the grooves and leveling down the peak between them, this is what I got. The idea of boot grips on an N-Frame is sort of a chuckle, but these are about as good as it gets for me, without rounding the heel of the butt and notching the toe.
.jpg)