I don't have the capability to post pictures but some makers you might look up are D. Funk, D. Stroup, and P. Resor.
I think you could use any "plow handle" stock profile or even a "cane handle" that suited your fancy, maple or walnut. A lock like a Queen Anne (pistol size), a small Siler, or a Davis Becky would be appropriate. An L & R Durs Egg is ok style-wise but is a little large for a pistol. The L & R Manton is of too late a period. Another option might be the Chambers gun maker's lock. Locks lost the tapered tail and evolved to a rounded profile as the end of the century approached. A "Maslin" style is most appropriate.
The barrel can be full octagon or turned octagon to round and be appropriate.
Furniture can be brass or iron, with or without a butt cap, with or without a nose cap. If you wanted to go really fancy, silver was also used. Earlier pistols had fewer inlays than those made closer to 1800. There was usually a little carving behind the tang but no carving at all also fits the period.
I think you can make whatever you want in a pistol and let the lock-style determine the historical period.
Hope some of this helps.