In all seriousness, here is what I would do.
50 gallons or less = Hand mix. Best possible way. Shovels in a kiddie pool, tarp or on strait concrete. At my old place, I would hand mix yards of soil on my concrete. I would rinse the concrete first, then plop down the soil.
50g-2 yards = Hand mix. Concrete mixer.
2-50 yards = Hand Mix. Concrete Mixer. Have your soil yard mix the soil. Mahindra's. John Deere.
50-1000+ = Custom soil mix from the yard, tractors.
Last year I hand turned 40+ yards, and moved 40+ yards of fresh soil by hand. Truck, Wheel barrows, shovels, and determination. I had the load dropped down the street, (access issues) then into my truck, then into wheel barrows, then into
smart pots or beds.
To answer your question about the plastic kiddie pool, I would call a local small pool supply store. If they don't still have one in stock, they will order you up one. I know Amazon only has blow up type, as the shipping is most likely too expensive. Or just buy extra in the spring, but that isn't going to help you now.
Or just buy a tarp.