Another minor problem in switching rear sights, is the issue of the correct screws.  (The 1901 sight requires a peculiar front screw. The 1892 & 1896 sights have a longer front screw). The various 'short' screws will generally interchange.

Reproduction sight screws and sight blades can be purchased from S&S Firearms, Glendale, N. Y.

The KCA Classifieds list a vendor, who makes reproduction hand-guards. The reproductions are expensive and not as nice or close fitting as a good original, but, better than nothing.

There are also parts sellers listed in Classifieds, who might be able to help with original items.