My parts books are literally from the last century.
According to my manual, they used to offer a .265" (M&P serrated), .312", a .400" smooth and a .500" serr trigger for these revolvers. The .500" "target" width trigger is not listed but I know they made one at some point because I have seen them.
Numrich lists some of the current triggers on their web site, but their latest schematic is for the 29-5.
29-5 Accessories | Numrich Gun Parts
Power Custom also makes a wide, smooth trigger for these models:
Power Custom Trigger S&W K L N & X-Frame Revolvers A2 Tool Steel the