Ok, so we get - both figures, not only costume part - https://www.amiami.com/eng/detail/?gcode=FIGURE-194472 - arouns 23k JPY (for 2 - TWO figures)

Underwear option - https://www.amiami.com/eng/detail/?gcode=FIGURE-194470

Normal clothes option - https://www.amiami.com/eng/detail/?gcode=FIGURE-194471

If you like both - the best and affordable option is to get full set - you will pay way less.