Everything you need to know about health in Tonga.
Feminine Hygienic Products
You can find feminine products on any relatively large island, Vava’u or Tongatapu would definitely have some in drug stores.
The local women I lived with do not use pads or tampons, they use some kind of natural cloth they make themselves. The island I lived on was also a two-hour boat ride away from any larger island, and they would only shuttle over to the large island once or twice a week if the weather permitted.
Birth control is taboo in Tonga. Women do not talk about it. There is a blue drug store on the main road in Vavau that is run by New Zealanders and would most likely carry it.