What is the ruling on buying clothes from stores that display immodest women's clothing on full mannequins, and is that considered assisting in sin?

Making and using statues is forbidden in Islamic law. This is based on what was reported from the Prophet, peace and blessings be upon him, that "the people who will receive the severest punishment on the Day of Judgment are the image-makers," and that "those who make images will be punished on the Day of Judgment, and it will be said to them: 'Give life to what you have created.'" Furthermore, Ali ibn Abi Talib, may Allah be pleased with him, ordered the effacing of statues. Therefore, using statues to display clothes is a reprehensible act that must be denounced. It is preferable to buy from shops where such reprehensible things do not exist. If that is not possible, it is permissible to buy from them due to the widespread affliction.