Is it permissible to sell clothing requested by Muslim women in Canada—such as long blouses, loose trousers, and skirts—knowing that they do not fall within the category of lawful Islamic dress, and that not selling them would lead to the shop incurring losses?

Islam does not prescribe a specific type of clothing for women but rather sets guidelines for it. If the clothes mentioned in the question do not meet the Islamic requirements, then it is impermissible to sell them to someone who is likely to wear them outdoors, as this constitutes aiding in sin. Whoever fears Allah, He will facilitate the means of their sustenance, and whoever abandons something for the sake of Allah, He will compensate them with something better.