Xita is a brand well established in Vietnam and their shop is on 150 Ly Tu Trong. They are having a special collection for this celebration season and is not that expensive, 1.5 – 2M the dress.
Laking House: They dont have shops, you have to order online via Facebook messenger or by phone. It is really cheap, 300k-500k for the top and around 800-900k for a dress.
KyO Tran: The shop is on 407 Nguyen Dinh Chieu in district 3. Prices are around 1.5M the dress.