A recent discussion in another thread addressed this. The concern in that case was not having to lift heavy jugs to pour into a gravity feed system, but the problem was largely the same.
The upshot was this:
Using another vehicle, say your TOAD in your case, equip it with a
50 or so gallon potable water tank. There are many to choose from. Just toss it in the trunk, bed, or wherever. If you're handling jugs, do this instead. Size the tank to the space in your vehicle, but even a Honda CRV could carry 50 gallons easily - 450 pounds including the tank. That's the equivalent of a driver and 3 passengers.
Then, use either a 12 volt pump powered by your TOAD (while running) to transfer the water or better yet,
use a 120 volt pump powered by your generator to transfer the water. The 120 volt pump can easily overcome any "lift" or resistance issues as you connect to the standard water inlet on your rig. And it can double as a "garden hose" for washing toys, and so on.
Empty, the water tank weighs only about 30 pounds, and hoses and fittings to connect the pump to the tank can be attached and detached using quick connect fittings, as can the potable water hose to connect the pump to your rig.
I boondock regularly, and I've spent years hoisting 4 x 7 gallon (60 lb.) jugs to dump water into my holding tank. This year, I'm going to make the switch to a system like this and double my extra water supply to boot. I can throw the tank in my TV truck bed, fill it, and transfer from the tank to the RV with no more lifting and carrying. And, since I always boondock, I'll finally get to use my potable water hoses that I bought years ago and never use.