In 2019 I attended the Yaama Ngunna Baaka Corroboree Festival in far western NSW. There were several hundred people camping out. Being a tech person, I took along a collection of solar panels, and power banks, to charge people's gadgets. What proved most useful were power-banks with attached fold-out solar panels. Kmart have one with an 8 Watt solar panel and 15000mAh battery for $55. There are higher power panels and batteries available, but then there is more to carry, and more cables to connect.