Transponder keys can either be ordered from locksmith shops, dealerships or department stores. Transponder keys are more expensive than standard-cut keys due to the special chip inside of them, which also needs to be programmed before being used. Although department stores can provide a shell, dealerships and locksmiths have the equipment to make the key work on its respective vehicle.
There are several different types of transponder keys, some of which may require a battery, while others don't. Locksmiths are seen as the best option in regards to transponder key replacement, as they are generally less expensive than dealerships while offering the same type of service. Locksmiths can be found by searching websites that provide business listings.
The next best option is to use a dealership. Dealership OEM transponder keys are really expensive, often costing in the hundreds. However, a dealership is able to properly program the key so it works on the vehicle.
The last option is to try a department or specialty store. These stores generally sell bare bones transponder keys that can be cut, but not programmed. Although the purchase price of the key is less expensive, it will still need to be programmed by either a dealership or locksmith.