My ROA shoots 6" high even when the adjustable sights are adjusted to the lowest level.

I've read the blade in the rear sight can have the notch filed down another 1/16" for a bit more adjustment, but I'd like a spare sight blade before I start bodging things.

Does anyone know if the adjustable sight on the ROA is unique to that gun, or is it the same sight as on another Ruger gun ?

Is there a 3rd party rear sight that can be fitted in the place of the existing rear sight ?