I think one of the posters said the right thing. Rabbonim in the neighborhood should enter the dress shops and speak to the “FRUM” owners directly. They should have a real conversation and they should let them know that as frum owners they are misguiding the kehilah by bringing in and selling them clothin items that are less than tznius and promoting goyish attitudes. There is nothing wrong with being stylish, but by doing so while in addition being untznius they are sending a message to the general public as well as to our youth that you can’t be stylish and tznius at the same time.
The Rabbonim should be very clear, obviously they cannot control what the department stores sell. But they can advise their Kehila members which stores to shop in and which stores they should absolutely not shop in. Store owners can absolutely ask their suppliers to get them the same styles with longer skirts, longer sleeves, etc. If they don’t ask, they won’t receive. If everyone has the same requests, their requests will be honored.