A lot of the farmers around here use something similar for watering livestock that are too far from running water or creeks. They are poly tanks in a cage that they haul on a trailer or the bed of a ton truck. I think they are about 500 gallons. My SIL is talking about buying one for his new garage.
I have options to check out now. I’ll check out the portable tanks, the Generac, and a few others.
If I notice that we are going to have high winds or a storm, I have been filling the bathtub with cold water to flush the toilet. All it takes here is a high wind and we have trees all over the powerlines.
T.C. Hopefully you don’t, but if you run out of water to flush, do your last flush and put two plastic bags in the toilet. Fill it with Sawdust, or cedar bedding, or cat litter and use that. Do not let it get too full before you pull it out and replace the bags. Use it until you get your water back! (Of course, you could do it the 1800s way and put up an outhouse!