I have a project gun, a trapdoor with breechblock marked "1878" and the hump-backed rear sight.  The stock is busted up around the lock area and I am working on rebuilding it.  Metal finish is "patina" brownish.  The lock is very good, bore is pretty good, and I am missing remarkably few parts, but need:
an extractor,
and the sliding elevation bar for the rear sight.  I think this is called a "buckhorn" sight, apparently consisting of a top, bottom, and spring assembled with 2 screws.
I do have the ladder, but if there was an assembled ladder with slider, that could be swapped out.
I realize this _should_ be on the WTB part of the classifieds, but for the moment I cannot post there... yet.
So, I am looking for leads where I can find these parts.  So far I have struck out.  any help would be appreciated.