You don't say what your situation is but if you have mains (marina) electric
power then there a number of small benchtop stoves that may suit.
Or if you have a generator
then I saw a 500W stove on ebay that may work. Despite the numbers matching I found a 1600W generator
won't run a 1600W stove on even half power (Don't ask how I know...).
Other than that there are small camping stoves that could be used in the cockpit