for battery.. I got one spare and an external charger which is very good for travels. it is expensive for just plastics but for the size I think it's worth it. At first I thought it was only the charger, but it also comes with a battery. I can't remember if it came with anything else, probably not. but it's not like you don't have a micro usb cable and wall charger laying around :P
if you don't care about having oem batteries, the wasabi brands are known to work well and are cheap.