الجواب وباللہ التوفیق

Although wearing such clothing is considered a sin and an act of lewdness but the business of selling such clothing is considered makrooh due to being an act of cooperation in the sin. As the cost for buying the clothe and having it stitched into these pants or leggings, in itself is not an abominable act, therefore, such an income will not be considered haram rather it will be considered makrooh. Therefore, it will be better to refrain from getting involved in such a business.

فإذا ثبت کراہۃ لبسہا للتختم ثبت کراہۃ بیعہا وصیغہا، لما فیہ من الإعانۃ علی ما لا یجوز، وکل ما أدّی إلی ما لا یجوز لا یجوز، وتمامہ في شرح الوہبانیۃ۔

(الدر المختار، کتاب الحظر والإباحۃ / فصل في اللبس ۶؍۳۶۰ کراچی)

فقط واللہ اعلم بالصواب