True, this particular design hasn't appeared
in an episode, but one can't have a swimsuit Joker without a Swimsuit
Harley.
The main body is from a Mulan figure (affectionately called "Underwear
Mulan"), while the head is a cast copy. The skirt is sculpy
with liquid plastic poured over it to keep it smooth. The dots are
actually stickers, available at office supply stores. They might
fall off in a matter of months, but I dread the thought of painting
all those circles.
For those of you who are armchair costume historians, her outfit
is based on swimsuits of the the 1920s so she would match Joker's.