Autoparts store or online.
I know advanced auto has them for sure
You need an h4 bulb and it will plug right in
Make sure you get the silver star ultra, and check the back of the package to make sure it is the brightest model. If you don't like it then you are only in the hole 20 bucks or so and you can then go big for led or something
And you can send me the silver star for a spare lol
You can buy only one if you want to also