One great fem Harry and Newt Scamander fanfiction is 'The Unlikely Bond'. It beautifully weaves their characters together in a world where magic is both a mystery and a solution. Another good one is 'Magic's New Path' which shows how fem Harry's unique perspective and Newt's love for magical creatures can create an interesting adventure.
There are quite a few out there. 'Fem Harry and Newt: The Magical Alliance' is a fanfic that I really like. It starts with fem Harry accidentally stumbling upon Newt's case of magical creatures. This leads to a series of events where they have to work together to protect the creatures from dark wizards. The author does an amazing job of portraying fem Harry's strength and Newt's compassion. Another one is 'New Horizons with Fem Harry and Newt' which explores a different side of the wizarding world through their eyes. It's full of vivid descriptions of magical places and creatures that they encounter together.