Where can I find authentic soccer jerseys in India?

I would try eBay. alot of those guys ship internationally. so I am pretty sure they would ship it to your place!
If you are in Chennai, goto Burma Bazaar!
don't worry I understand the soccer craze is yet not over you are real soccer fan .if you living in any of the metropolitan cities you can visit the fila and adidas showrooms.you can even visit all the smuggle markets like china bazar,but hey I cann't gurantee if they are authenticated.
I dont no even though im indian
no idea...you might be better off just trying to get something online.