How can you say exactly that the battery is dead, may be your charger is unable to charge the battery properly. Yes, laptop will power on with charger, but if its not providing proper vatts / amps required battery wont charge. Then there might be a problem within the laptop as well. Anyhow, the first thing to check is your charger.
You will not get genuine batteries here, you will get 1st copy batteries (with 3 months warranty) here which works fine. Price would be around 4/5k in Lahore. I have mentioned in my another post as well, that 1st copy is the best you can get, someone may sell the same to you for 7/8k claiming its a genuine one. Without taking names, I know some manufacturers office selling same chargers / batteries for much higher margins. I guess, there are people who get satisfied by paying more