This may seem a tad crazy, but I built one myself years ago, and still use it occasionally on camping trips. I built an AA powered boombox, and included in it a USB charging port. The parts you would need would be a 10 AA battery holder. A standard 12 volt socket and a USB car charger. Then just find a little plastic box to mount it in, and install your 10 AA rechargeable batteries.

IDK where you live, this one is great for hot climates. I personally own 2 of them here in Florida. I assume you have a lighter port in the 2018, so something like this could help you get more USB ports if you need them.