You might want to look at the 'Sense' and 'Sensibility' series at DAZ (though thats more regency), and the MFD has some suitable textures as well.  There is also an outfit for k4 (vintage girl) that make a nice prairie girl style look.

I think someone made some bonnets at sharecg and you can always ask the '20th century clothing' thread at DAZ, which despite the name is frequented by historical clothing renderers and clothing makers.

Actually .. they started this wiki so you should have a rummage . Not sure what all is in there.  http://3dhistoricalcloset.wikia.com/wiki/3D_Historical_Closet_Wiki

Cooincidentally I have an 18th century ish day dress I'm just about to start promos for. once I finsih a few little edits. It's not wholly accurate, but its close. The final version will have a custom magnet set to add proper corsetry shaping to clothing and model. It does have a couple bustle and shape morphs to fit a few differrent eras and styles.

Lyrra