How is this: Amazon Samsung Galaxy S3 i9300 Battery EB-L1G6LLUCINU
Only issue with the above(amazon) is its model number is EB-L1G6LLUCINU whereas the actual model number is EB-L1G6LLU, so what does CINU stands here for?
And will I get 6 months warranty if i would buy from your first link or from amazon?
In Samsung's dictionary INU and INS both mean India. I have forgotten what's the difference between those two, but its nothing that important which will make that battery incompatible with your phone.
The link you provided seems very original to me, also the seller has good ratings, you can safely go on with that. Still, to be safe, send that seller a message asking about whether it will work or not on your phone, and say beforehand that you will return the product in case it doesn't work, that way you will be safe.
The links I provided, well the sellers do mention that they will provide six months warranty, so that's a good thing, but the Amazon seller doesn't mention anything about warranty, so I think buying from Ebay will be a safer bet here, and I can also assure you they will provide you a VAT paid invoice too. But same rule applies for Ebay sellers too, ask first, then buy. You can never be too safe with online purchasing
Best of luck.