Since your revolver, like many J-frames, has it's sights integrally milled into the frame (rear) and barrel (front), changes won't be easy.
A good gunsmith could certainly insert and secure a rear sight into a milled notch where the existing tunnel sight is, or perhaps weld and re-machine a 'V' sight, but since the frame of that gun is aluminum, both would be rather specialized work.
I have a 642 and have investigated getting the front sight swapped for something better (i.e., not silver and small) and finally decided the smartest plan would be to buy a different gun. Swapping sights on these aluminum J-frames is just complex, and therefore expensive.
Larry