This hydration pack. It's got a decent solar panel and comes with a fairly large battery pack that you can use to keep your phone charged. I was recommended this by someone at the forest that had one and let me use his charger when my phone died and I had no idea who was playing when the first day. It's going to be clutch this year https://www.amazon.com/dp/B011K27D9W/ref=cm_sw_r_cp_apa_RYDWybED76PKR