Front sights should be available. Try Numrich or Jack First Gun Parts. You will need to measure the height of the existing blade. I would call by phone to make sure you get the correct one. You might check on Ebay also.
There are aftermarket replacements also, if you are not opposed to using or adapting one.
Numeric would be a last resort...I'm calling Jack first today...
All I can seem to find in replacements is the blade. Mine is a blade and ramp with 2 pins that attach it to the rib..