Reference: Fataawa al-Lajnah ad-Daa.imah lil-Buhooth al-‘Ilmiyyah wal-Iftaa., – Volume 13, Page 108, Question 1 of Fatwa No.18409
Question: What is the ruling regarding one who sells and trades in women’s clothing, especially that which is tight [fitting], and also under garments?
So is there any sin upon him if a woman was to wear such clothing and go out amongst the people?
Response: It is allowed to trade in permissible women’s clothing. As for impermissible clothing, such as that in which there is a resemblance with the disbelieving women, then it is not permissible to trade in it, since this constitutes assisting in sin and transgression.
And with Allaah lies all success and may Allaah send prayers and salutations upon our Prophet (sal-Allaahu ‘alayhi wa sallam) and his family and his companions.