Is it possible to have a thin heating element like a silicone/rubber pad, a foil, a wire or a wrap that would cover an area 4 x 6 inches long, heats to 120 + degrees, can run off of a small battery (12V or less) and last at least 30 min? Is the technology out there or would you have to change it to a greater power source like 120V to achieve this? The answer I have received from my research so far is that it would take 150W of power to heat something this size to 120-130 degrees F and require a large 12V battery with min 10AH to last 20 min. Is this the best solution? Chemical heating pads are too thick but achieve the right temperature and for safety it has to be low voltage. Any ideas?