Hello Dave,
Yes, send me your sight and I will drill and tap it like our XA series sight. $20 which will include shipping and an extra aperture of your choice.
The idea of a threaded hole in the dovetail filler isnt a bad idea... I'll kick that one around. Might be a good choice with the Skinner "Express" sights.
The aperture will not fit in one of the sight screw holes. I could make an adapter that would allow an aperture to be kept there but it would only work with the 1895/336 standard sights. Our 94, Tactical, and Express sights would sit to low to see over the top of such an arraingment.