I don’t have a single dedicated map for what you are looking for, but if you look at pages 108 and 112 of “A Birder’s Guide to Washington (Second Edition)”, you will find two maps that cover each of those areas (i.e., Skagit Flats (Skagit river delta), Samish flats (between Edison and Samish Island)). You probably already know about this, however. If you find a single dedicated map for both those areas, please let me know. I often visit both areas during the same trip. Thanks!