I use a normal flash drive (https://smile.amazon.com/gp/product/B07BPKKTGL/ref=ppx_yo_dt_b_asin_title_o05_s01?ie=UTF8&psc=1) with a USB A to USB C cable (https://smile.amazon.com/gp/product/B0194WSKOM/ref=ppx_yo_dt_b_asin_image_o05_s01?ie=UTF8&psc=1) .
It needs to be MS DOS FAT formatted, and you can use file types MP4, mp3, AAC, OGG, and 3GP