Do know that there are differences in the screw spacing. I have bought off Ebay where I was able to confirm the dimensions with the seller. Also what vintage of N-frame will determine if round front or square front. What specifically is your gun? MXX-Y? I have a couple back home.
The radiused rear sight is the hardest to find. The squared one is easy to find. You can very carefully radius the square one to fit the inset and if done carefully the screw hole lines up perfectly.
They’re still using the radiused model on current production guns. If the OP were inclined he could likely get one from Brownells or Midway, barring that a call to S&W would almost certainly produce one. The factory would also ship the one with the correct height rear blade.
