You could easily dovetail the rib and mound iron sights, perhaps a thick blade for the front & U or V notch rear.
Or- a wide V filed into an iron sight something like this.
File it down to the correct height and a small 45 degree angle will make a bead in light.
https://www.trackofthewolf.com/List/Item.aspx/874/1

and this: just file it out to a wide V
https://www.trackofthewolf.com/List/Item.aspx/880/1

The dovetails need only be 1/16" deep. A safe sided 30-corner file is used after knotching vertically "almost" the width needed.