I have a M&P 340 that comes standard with XS Dot Standard sized sights. I like them a great deal.
They can be retrofitted to X42s but I think XS on their website states that they must be installed by a "trained professional. I think you have to grind the blade sight down substantially to fit the dot.
You might like trying laser grips for point shooting. I don't find snubs target revolvers and although at 10-50 feet the sight can work to attain some ok groups.
For personal defense I would rather be profficient at point shots in a 10 inch COM a laser can provide that training "feel" for the time when you need to point and shoot w/o them.
Goal 5 rounds, five seconds at 5 yards.
Essentially it would look something like this upon completion.