Your first link shows pictures of different plugs that various piece of equipment (ozonators, blowers, pumps etc,) used in hot tubs have, that plug into the controller of the hot tub. These are NOT the main plugs used to supply power to the entire hot tub. Hot tubs, 220v, don't have plugs. They also use far more power than any of your converters would supply....and even if there was a converted that would work, you'd need an electrician to run a MASSIVE 110v circuit to it in order to supply enough current. It would be FAR cheaper to just have an electrician run the proper 220v circuit directly to the spa.
There's no short cut here. You'll need an electrician.