Could you research a small solar panel? My daughter uses one to power the battery for electricity to fence in her horses. This might be cleaner than paraffin, where the main danger, I suppose, would be poisonous fumes.
However, there is a book 'Artificial Incubating and Brooding' which was originally published pre-1923 in America, which is now available as a paperback reprint, which gives details of how to incubate and raise chicks using paraffin brooders. I have a spare copy you are welcome to have, if you'd like to PM me with your name and address.