Holy crap, you could drive a truck under that thing. That’s a nine cell battery for the MSI Wind netbook, which is available on Ebay’s UK site according to a post in the MsiWind.net forums. The item ships from China for a grand total of around £70 – roughly $115 in US dollars.
Owners of this gigantic lump are reporting over 6.5 hours of battery life. When I tested the six-cell MSI Wind, I was able to get a little over five hours before having to recharge so I’d almost think you could squeeze 8+ hours out of a nine-cell battery with everything tweaked to maximize power consumption.