Hello, Tomorrow! In one of the amateur radio magazines I read, an article appeared (to which I cannot link) about a fuel cell power supply about the size of a small suitcase. It supplies 40 watts at 12 volts continuously off of hydrogen cylinders that can be recharged easily. Its pricey right now, about $6000 last summer. The company that produces it is called Jadoo Power Systems. Here is a link to another article on one of the devices Jadoo produces.