Replacing the BIOS battery in my Asus G53SX-NH71

My laptop's main battery has been dead for several years, but it wasn't a problem until just recently when it started blue-screening occasionally and eventually stopped booting entirely. I've been told that it's likely due to both the main and BIOS batteries being dead, causing the BIOS to freak out. A replacement main battery is on the way, but I'm uncertain of what exactly I need to replace the BIOS battery. Judging from various pictures I've seen of the G53SX motherboard on Google and eBay, it looks like a button battery that I could find at a local store. However, even if that's the case, I'm not sure which specific type fits my laptop. Can someone point me to exactly what I need?

Thanks.