Welcome to the Forum,
The revolver you have pictured is not wearing a S&W factory adjustable sight. It has the Extreme Duty fixed sight from Cylinder & Slide. That rear sight is not available with tritium inserts. However you could purchase one from C&S and send it off to the custom shop at PT Night Sights where tritium vials could be installed.

Meprolight offers a replacement rear blade that goes on the existing factory adjustable sight body. My model 627 has a Meprolight rear sight blade on it and a front sight made for the S&W Interchangeable Front Sight (IFS) system.


Since you do not picture your model 19, we have no idea if it has a attached front sight, red ramp front sight or pinned front sight. Meprolight makes two different tritium front sights. One is meant to replace a pinned front sight while the other allows you to knock the colored insert and glue in a piece containing a tritium lamp.

If your front sight is attached and has no colored insert, the revolver could go to PT Night Sight's custom shop and they will install a tritium lamp, or you can have a gunsmith grind the existing sight off and cut the barrel rib for a pinned in sight. With a blue revolver this is no big deal. If the revolver is nickel it is another problem.

The grips pictured in your photo above are Hogue finger groove grips made of Coco Bolo. That J-frame, model 36 has a round butt frame. Odds are pretty good that an older 6" model 19 will have a square butt frame. S&W did not go all round butt until mid 1990s.