I have a better idea for all who feel they can’t find tzniusdik clothes in stores. Teach your kids to sew and be creative!!!! There is nothing wrong with a fifteen year old, designing her own clothes or fixing her own purchases to make them tzniusdik by using her own imagination and adding some trim to the bottom and sleeves for length, or adding a pretty piece of fabric for a dickie, etc.
In addition, they can buy something they like in a larger size and then take it in so it fights properly without being too tight, yet still maintaining the style and elegance it was designed to have.
We really should stop blaming the designers. We do not encourage our own girls to go into this field, so when clothing designers do not recognize our needs and produce for us, we have no one to blame but ourselves. Yes we have frum people in the clothing business, but at best they have their manufacturers tweak the designs they already produce and not necessarily design for the modest crowd.