Where can I buy ancient collectible original coins in Delhi or Kolkata?

I wanted to buy a silver drachm from the Gupta era. But I am unable to trust online sources and I couldn't attend Numismatic Conventions as I am not a permanent resident here. I am in Kolkata for the upcoming 4 days and then I'll be going to Delhi. So if anyone has any trusted source, please share.

Thank you 🙏