When it comes to being portable, the Optimus H-1322 Portable Space Heater is one of the most popular choices. It is a small and can be easily transported from room to room. There is even a carrying handle for easy portability.
As far as other heaters that do not require power, most small portable heaters do not have a fan. The regular Mr. Heater Buddy, to my knowledge, has no fan, and therefore requires no power.
Forced portable air heaters are really powerful space heaters that are mainly used for industrial, factory, or agricultural use and are very economical and energy efficient. Forced portable air heaters work really quickly and for the amount of energy they use and they advanced technology they are really inexpensive. The most common type is called kerosene BTU forced portable air heater that is sold in a lot of online stores for a low price and in most cases free shipping, so you don’t get tagged with the extra charge to bring such as heavy unit home.