Do these exist?

Either falchion, scimitar, or kukri of banishing?

If so, what do they go for and does anyone have one for sale??

They do not exist. There is only one slashing banisher in game and it is obtained by beating the Abbot raid.

banishing is on pierce/blunt not slash except for a raid drop ls from abbot :)

I guess that explains why I can't find one. Bummer..