If you've lost the charger for your Nexus phone or tablet, or just need an extra one, Google is now selling a reasonably-priced replacement.
The “Nexus Charging Accessory” is available for $15 through the Google Play Store. It'll work with any Nexus phone or tablet, and presumably any other Android device that charges over mini USB. There's nothing particularly special about it compared to other chargers, though it does have “Nexus” branding on its square-shaped power block. Google doesn't specify the size of the included mini USB cable.
Cheap replacement chargers for Nexus devices can otherwise be hard to find. Asus sells a replacement Nexus 7 charger on Amazon for $30, but that's twice the price of Google's offering. A search on retail sites and the Web turns up no official replacement chargers for the Nexus 5.
Inexpensive third-party chargers are an option, but then you can't be sure whether they'll charge as quickly or efficiently. At that point, you might as well just use the charger from an old Android phone.
For those who don't mind spending a lot more on something a little fancier, Google also sells a $50 wireless charger that works with the 2013 Nexus 7, Nexus 4 and Nexus 5.