I have been unsuccessful in finding an aperture sight for my 1905MS. So, I decided to roll up my sleeves and try to make a bolt shroud aperture out of sight bits and pieces that I had in my shop.
I bought an extra bolt shroud from Sarco for a Greek Mannlicher. I had parts from a Lyman tang sight and spare aperture from a XS Ghost ring.
I cut the tangs off of the sight and flipped it so that the upright would be perpendicular. The sight was silver soldered to the bolt shroud. The upright was harder. The XS has a proprietary thread size so I could not find a tap. I used the decapping rod from an old Lee loader and drilled the center out. I silver soldered the XS sight dovetail to the top. This allows me to adjust vertical height by screwing up or down on the aperture.
After determining the proper height of the upright, it was soldered to the sight.
It was not easy soldering the upright without loosening the aperture attachment. In retrospect, it would have been easier if I would have had a peep aperture with a standard thread size. The upright could have been tapped to the thread count.
I plan on using some blue Loctite to maintain the aperture setting.
Sorry for the long-winded explanation. I was fortunate enough to have enough "stuff" at home to cobble this together.

https://www.imagebam.com/view/MEB8UZ5

https://www.imagebam.com/view/MEB8UZ6