i don't think there is enough material on the top of the slide to cut a dovetail. even if you did, i think most comercialy available rear sights would be wider than the gun because they are all made for larger guns. painted my sights and they are much better.
Remember, its a pocket pistol.........you dont want or need additional protrusions to hang on anything......The gun is fairly accurate as is... Painting the sights is the way to go..... just my opinon however....
if you wanted a pocket 380 with sights then you should have gotten the one on the left, not the one on the right!
as the others have mentioned a lot of problems concerning your idea!
you might want to search the thread 738 sight enhancements, there is a multitude of different things there that may help you.
If you notice in the picture the TCP 738 sights are painted with a glo in the dark paint and they show up some better, still not Sig 238 sights though.