Healthkart is the probably the best place! I have a couple of friends who speak fondly about it.
Go to Buyceps, it's the store of Sahil Khan's Divine nutrition protein. It's very authentic, got the trust of Sahil Khan. There's a store in sector 7 Dwaraka, otherwise you can also order it online. If you want more popular brand, then 'my protein' is also good.
Don't know exactly about the offline stores but online one is Healthkart
I don't have trust in shops instead I buy them online from trusted sites like HealthKart or Nutrabey
Actuallu first consult your trainer and then you can opt for online supplements as corona is going on.
Healthkart is good otherwise ask your trainer to get one for u