G-strings have a range of styles and can combine fetishistic aspects as you like.
A Gothic corset dress does not have to be fetishistic.
At Top Drawers, they have a good selection of California muscle thongs and briefs, some more fetishistic than others.
Much of what you'll find here is less specifically fetishistic and more plain sexy, with a dash of raunchiness.
A cross between a jockstrap and a thong, with an added strap across the rump makes this both practical and gently fetishistic.