This is probably a very niche suggestion for a very niche gun, but I came up with a low-profile unobtrusive way to get a basic ‘back up sight’ arrangement on my PS90 TR version (the only variant without built in backup sights)
I used a low profile picatinny front sight up front, visible through the micro dot.
I took a black matte decal adhesive and traced a circle with a penny, exact size of the rear optic lens, and cut a small fraction of the bottom of that circle, giving me a sliver of about 1/5 of the size of the rear sight window. I cut a V notch into said decal, and carefully applied it to the lowest part of the rear optic lens.
It was actually pretty close to dead-on at 15yds. I lowered the front sight somewhat, and boom, basic no-frills minimalist sight system for a gun that is otherwise difficult to equip such an arrangement.