Save videos directly to flash drive in IOS 10.3.3

So I have a small YouTube channel. Ive been trying lots of different cheap cameras ive had lying around to see which is best. My Dad just got a new iPhone, and I want to start using his old iPhone 5c as my camera. Problem is, it only has less than 3GB of storage with all unnecessary apps deleted and no photos or videos. I need to use an external storage device (Lightning flash drive) to store my videos on. Theres not even enough storage for a single longer shot tho, so I need to store the video directly on the flash drive when recording. Can this be done on IOS 10.3.3? If so how? Thanks!

Edit- Im gonna buy a Lightning flash drive. Is there a professional camera app with manual functions( like ProMovie) that lets you save clips directly to a flash drive?