Good news for all, that love their SP101.
If you have a SP101, with 4” barrel ( only model ) that has the HiViz front sight, and want something different, the front sight dovetail, is exactly the same as a Ruger SR9. It is however a narrower profile, and requires trimming the sides down with dremmel or grinder or whatever, then insta blueing the exposed sides of sight dovetail.

As my eyesight has deteriorated over the years, I’ve wanted something different , and easier to see than my old , faded encapsulated HiViz FO. I’m tired of trying to paint a little white, around the fiber optic. I want a green tritium, in a bold white dot. I want a TruGlo TFO or TFX. Whatever… Ruger doesn’t sell it. HiViz , TruGlo , Meprolight … no one makes a sight for SP101. You’re stuck with it. But they all do for Ruger SR9. ( just that the dovetail itself is too wide and needs to be trimmed down )

Spending time in LGS, looking at sights … measuring sights …measuring dovetails on various pistols… talking with well known custom gunsmiths… landed on the SR9 sight.

I ordered a cheap, $10 factory replacement SR9 front sight from Ruger, it arrived, and it fits…. And is same blade height, too.

Now to find the sight that I want. The only downside is there are no options, that I’ve found yet, for the adj rear sight. HiViz does claim that their FO rear for GP100 , Red Hawk etc etc will fit SP101. It does NOT, or at least the one they sent, does not.