I've placed an order for a 10 gal RV water tank and a connector kit with the hoses and adapters needed.
I'm holding off on buying the pump... I want to see if it's possible to move the cold water purely by gravity-feed... in which case we might just avoid hot water when not connected to a water source...
...or I will buy a pump later. We'll see.
I'm a little weary about having to run the electric pump at the same time as the electric hot water heater.