Check out Sunnbattery.com I was just there and that's the cheapest I've ever seen a sony battery for ($99). I'm going to order one from them just as soon as I get some extra cash. But I've ordered other batteries from them before and there service is awesome. I would call them and do the order - they sent mine out like the next day.
Hope this helps....
SunnBattery F-series Sunnbattery.com
Gary