Google is now selling a new wall charger with an AC adapter and a USB cable on the Play Store for just $15. Unlike conventional wall chargers, this one is pretty powerful at 9 watt (1.8A) which means your device will charge quicker than usual.
For $15, it looks like a decent bargain considering what it brings to the table. The Play Store listing only mentions compatibility with the Nexus 4, Nexus 7 (both models), the Nexus 10 as well as the Nexus 5, with no mention of other Android devices. So it might be safe to use the charger only if you own either of these devices as the warranty probably won’t be covered it in the event of damage. But technically speaking, there should be no issues with any device which uses a compatible micro USB charging port.
Conventional chargers can take quite a while to charge a device from a completely dead state, so make sure you check this out if that’s one of your concerns with the current Nexus charger that you have.