The Williams FireSights are good for bright to dim lighting, as long as there is some light. I've got them on a couple of guns and they are good for these tired old eyes. As soon as I think my OSS is actually fixed I'm gonna get a set for it. I like the fully adjustable ones but they make fixed/windage adjustable also.
I think HiViz also makes a set at least for the front sight and usually the front sight is the one needed the most.
I have a Glock that I have put the lowest rear sight I can find on it and it still shoots slightly high for me and HiViz makes a tall front sight I'm gonna try on it.