zumo_2.0_android/app/src/main/res/drawable/switch_thumb_off.xml

<?xml version="1.0" encoding="utf-8"?>
<shape
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:shape="oval">

  <size
    android:width="20dp"
    android:height="20dp" />

  <solid
    android:color="#ffffff" />

  <stroke
    android:width="1dp"
    android:color="#e5e5e5" />

</shape>