Here are two "Lolly Pop" type tang sights that look really simple and useful to me.

The first one is a simple thumb screw from the hardware store with a hole drilled in it, and a knurled nut. It's adjustable for elevation, but not windage.





The second one is more sophisticated. It's adjustable for both windage and elevation. It looks to be factory made, but wouldn't be that difficult to fabricate at home.