I'm afraid they are OOP (is Evilbay your friend?) and I read they are quite *huge*, but Foundry female Revenant Elves have a definitively '18th C.' look:
To 'normalize' their ears would not be too hard; but, being Foundry, thay suffer the 'big feet' syndrome
Outpost Wargames' 'Wicked Lady' (taken from some movie about a highwaywoman, I think) looks like some female Zorro -not 18th C. at all, unfortunately.
Now, giving a tricorne (WF plastic?) to a mini immediately 'tags' it "18th C.", re hot Direktorix Katarin Lahmia: link
The new 'Jacdaw' figures are 30mm in the -debatable- 'Old School' style of the Tradition 'Willie' of the "60 which may not be of everybody's taste (and their sculptor emphasizes the 'caricature' approach), but maybe some can of use? link
Among the minis for Vesper-on Games Carnevale
link
the Barnaboti woman
and the White Dove
could perhaps appear as 18th C. witches?
Then you may also consider the Laughing Monk (ex Shadowforge) link 'Scarlet Woman'
(her pistol would not be too hard to convert) but she's a *big* "32mm".
Now, in The Real World™ people's tallness and shape widely vary (in 1/60 Pamela Anderson and Sigourney Weaver would differ by some 5mm) and you can play on the thickness of the base; so much the more as during games minis are not seen straight from the side but rather more from above.
And Freebooter Minis link do have some figurines, specially among their Assassins, with a 18th C. look
link
'Pirates' ranges also deserve to be explored (any Governor's daughter could made a cute witch).