You need energy (amp hours) to run as long as you are out there. You can bring batteries, or a generator and gasoline to meet that requirement. If you have other batteries you can borrow, that is the cheapest- it could be a car battery, golf cart, or power tool battery. People run them on 18V tool batteries, and a 30 AH X 12V battery has the same power as 20 AH worth of 18V tool batteries. If you have to buy something, I think an off brand or used inverter generator is your best bet. Power stations are basically batteries with an inverter, so they will be the most expensive option.