My 2018 Leaf S came with a CD player. But, the player was not included with the other trims in 2018. 2019 models may be in the same situation... Nissan is funny that way.
I have played around using USB sticks, old MP3 players, etc. and have had good results with them. The USB stick would mimic a CD, where each track is played in order, but you can still skip tracks, fast-forward, etc.