Today I have called Trijicon , XS, Ameriglo, and could not call Truglo ( not accepting customer inquires). Here is what I was told.
XS has a sight but the rear sight does NOT have a tritium insert. Can't see the point of a night sight that only has a front lamp.
Ameriglo is working on a specific sight for the Shield that will be available in 45 to 60 days
Trijicon sights fit but they are analyzing the sight height. The rep told me that with current sight Trijicon does not know what POI is for the current HD137 sights. May have a determination within a "few days" . Project on a fast track.
Truglo --- could not find a number on their websight . Had to submit questions VIA a customer inquiry form.
Next call will be to Heine and then warren.