You can obtain Hazel by naturally getting her in several ways: from the starter villagers in New Horizons, camping on mystery islands, or her visiting your own campsite. She also has an amiibo card easily accessible in the series 3 pack (mystery 6 cards, so a slight chance to get Hazel); you can find her in boxes at other people's islands via groups or posts specifically for trading or getting villagers. NEVER pay real money for those! (Especially since Hazel is not a very coveted villager.)