The button will be a pain to replace properly. We had a special tool to secure it in the frame. I needed one on my Mod 39-2 and I no longer worked at S&W so I used the above style hammer pin and sear pin instead. This was quite a while ago, I'm not sure but at the time I think I used a Mod 59-2 hammer pin and sear pin and shortened them to fit the 39. I'll see if I can get a pic of mine.