In a sense, the most “natural” replacement for lost estrogen is estrogen, which is a prescription product (like Premarin or Estrace vaginal cream, Estring, Vagifem, or the non-estrogen Osphena).
If, for a number of reasons, you prefer not to take that path, the next-best option is to maintain vaginal tissues by using a moisturizer regularly, two to three times a week. Moisturizers are designed to bring more moisture--no surprise--into the vagina to prevent the progressive dryness that occurs in menopause with the absence of estrogen.
One more option might be an oral nutritional supplement, Stronvivo, which some research shows improves vaginal moisture. It does this by improving blood flow, and that circulation also supports tissue health.