I bought a 2017 SL from Carvana which was delivered on Sep 20, 2018. It also had a missing SD card. Carvana told me to visit a Nissan dealer and have them charge it to their warranty company (SilverRock). No dealers wanted to do business with SilverRock. I just bought a SD card from a dealer and installed it myself. Cost me $125.76 in Ohio before tax.
Installing is easy. Insert card, turn on car, follow instructions.