If individuals want to buy public sector bonds in India, they can choose any one of the platforms:

Bank
Investors can buy PSU bonds on any bank's website authorised to sell PSU bonds. They will have to open a trading and Demat account with the bank.

When public sector undertakings create debt, it is called public sector undertakings bonds.

A public sector undertaking (PSU) in India is an entity (in the form of companies or public banks) in which the central or state government has a majority stake (more than 51%).