Purchased an Asus X58L laptop from Argos three months ago, I want to buy a spare battery but there is no part number on the battery, telephoned some companies but no help without a part number, contacted Argos, no help at all, wondering if they sold me an out of date product, can any one please let me know what the part number is for this model, all I know is that it is 11.1 volt 4400 mah 46 w, or how to get one, thanks