One of the amazon reviews is from an arranger keyboardist, using this portable power supply for his keyboards, amp, and a TC Helicon Harmony M. There's picture of his set up. Seems like a good solution for any event where power may be an issue.

https://www.amazon.com/Portable-FlashFish-Generator-Adventure-Emergency/dp/B07T48L6CF/ref=sxin_2_ac_d_pm?ac_md=1-0-VW5kZXIgJDIwMA%3D%3D-ac_d_p