EcoFlow RIVER portable power station with 288Wh capacity & up to 1800W power output.
Mine is now approaching four years old and is still invaluable for two days or more. It's not bulky and can be slotted somewhere on a barrow or left in your vehicle.
It's been used with the separately available solar panels and over a week abroad keeps everything I need from phones to leisure batteries charged. I see more variants are available now and prices have actually dropped by about a third since I bought mine. It's controlled via an app or the unit itself.
My version has two British mains plug sockets one can be boosted for higher drain electrical devices, two usb points, one a fast change usb point and one mini usb point, it has a 12 volt port and can also be charged from via your vehicle or mains . Charging takes a couple of hours from 30% which is low as it has gone down to over a week.
I just keep a small bag with various cables with the unit and power issues are solved.