I'm resident of Kolkata, all electrical hub of West Bengal, there is a place name Chandni Chowk which is the best market in West Bengal for electronics and I know there some best shops also because I am a robo Maker, I use all kind of batteries!
I assure u that u will get whatever you want in cheap price .
specially in this case I don't think that nobody is better than me , because I regularly travel those markets.