Melatonin is available in many formulations as a pill. It is very close to being "natural".... I think our bodies produce melatonin as part of the sleep/wake cycle. A pill would simply enhance that process. I don't find it to be of any help, but then I mostly don't have a problem going to sleep, staying there is another matter.
Sometimes the basics work, a warm bath half an hour before bed. A non caffeine hot drink. Even spraying some lavender around your bed is said to help as it is supposed to relax.