Any good website to buy replacement mobile battery?

I also want to replace my redmi 3s prime battery please help

Buy from service center only. Every 3rd party one would be a fake Chinese one. Thats why the ones in the service center costs twice as much. I figure if I am spending the money and going through the trouble to replace a non replaceable battery I might as well get an original. These batteries lose 50% capacity in an year if you are a heavy user. Even my rarely used phones are at 50% in 3 years. But then they start losing charge much faster.

I got my Oneplus One battery after placing a request at service center since the stock was very limited. There were local options as well ranging from 500-1100, however I went with service center option. It costed ~1.5k along with labor charges.