Depending upon for what purpose you want adjustable sights - an alternative might be to get Crimson Trace laser grips for your J-frame. I have them on my 442, and others have reported great results on other J-frames. They are adjustable to make the POA (the laser spot) fall exactly on the POI for each individual gun at your chosen range.
I agree with the others (and apparently with S&W) that if you want adjustable iron sights, you should go to a 3" barrel. The snub-nose revolver simply does not give sufficient sight radius for adjustable iron sights to be any more accurate than non-adjustable. I personally think the 3" is only marginal for accurate aiming potential, but your mileage may vary.