You can find replacement power adaptors for your cellphone at stores that sell electronic accessories, such as Best Buy or Amazon. These stores typically sell universal-style chargers for use with a variety of cellphone makes and models. They also sell car chargers.
Official chargers for the Apple iPhone can be found at the Apple Web Store or a retail location. Other brands sell chargers compatible with the iPhone, but Apple recommends its own brand. If you have to replace the charging cable as well as the power adaptor, make sure to find one with the right plug type. Apple changed the charging port starting with the iPhone 5. If you have an iPhone under warranty, Apple replaces the defective power adaptor for free.
There are four factors to look out for when choosing a new adaptor. These include the input voltage, output voltage and output current. If you need a charging cable as well, the connector on both sides may also be an issue. Most charging cables have a USB A connector on one end, which allows the phone to be charged via a computer as well as the power adaptor. If your power adaptor fails, you can use the cable to charge your phone via a computer if available.