Prop24 has good collection of stationary.
U Can order stationery from firstcry at good discount
There is also a stationary subscription box if you are interested. It is relatively new but looks promising. You can check their insta - paperquirks stationery
You can check out Bunk Pages or Fangled. If you are staying near Lajpat Nagar, Sita Ram Stationery is open and has some amazing stationery.
You can check out doodle family on instagram
Paper it stationery and 7mm fine paper stationery
Type7 Design, PropShop24, Scribbling Works are good options