Original sight screws occasionally show up on ebay.

Some vendors listed in the KCA Classifieds may be able to supply a correct screw.

S&S Firearms, Glendale, N.Y., has decent reproduction Krag sight-screws. Their catalog is view-able online.

Be patient, this is not urgent. Few people will know. You will eventually find a correct one or set.

Hints - Use your 'worst' sight-screw in the rear sight-base hole, where it is out of sight.

A set of reproduction screws or 'burred-up' spares are handy to have, if you are going to be switching sights occasionally.

BTW - Krag sight mounting screws measure .156"X 30 t.p.i. You won't find these at ACO or most Gun Shops.