Acer Extensa 5220 battery information needed

I need a new battery for Acer Extensa 5220, like this one

http://www.b2c-shopping.co.uk/m,acer,extensa-5220-200508,laptop-battery/

I need to know where to get it from in Islamabad and what its price would be? I need the price for 6 cell and 4 cell(if available).