I don't know where to find one, but I'm going to need one soon enough myself. That little pushbutton switch wedged up between the base of the fixture and ceiling is nearly impossible to reach without bending the frame on the shade. And no, you can't just reach up through the shade...it has a bottom glass on it. I've looked high and low and there is not a wall switch for this light in our 2016 27DSRL. Good luck in your search and let us know if you find a source for the shade.
Ode to the Forum Moderators
May the Mods grant me the serenity to accept the opinions of those I cannot change,
the courage to offer valid input to those who are open to another way of thinking,
and the wisdom to shut myself down whenever I get too in love with my own misconceived brilliance.