I would just look for anything that specifies it is genuine OEM and matches the OEM part number. I'm not a fan of generic aftermarket batteries; you may get lucky, but you could also get a crappy runtime or worst case an un-safe battery. (Think about how much actual energy is stored in a lithium ion battery and then tell me if you want to risk it being unsafe)
It looks like Anker doesn't make a replacement battery for the Nexus 4, but they typically have quality aftermarket replacements for batteries and power supplies (i.e. for laptops).