Saste Kapde Ka Depot Rk Puram. If you want reasonable things with good quality. Give them a try!!
There are plenty of fabric shops in Lajpat Nagar where you can shop for a wide range of fabrics at affordable prices!
Why don’t you check out Fabriclore.com they have a large variety of materials. I am sure you will find something that you can use for your dress. I would not suggest you to go out at this point of time to outsource fabric so Fabriclore is the best option according to me. Stay safe.