This popular bootable USB creator includes a "Download" script that allows you to select "Windows 10" and then pick "Build 14393 - 1607" from a dropdown. It downloads the file directly from microsoft.com .
Locate your desired edition (Home, Pro, Enterprise, or LTSB 2016). Click next to the specific architecture you need. Crucial Technical Specifications for Build 1607 download windows 10 version 1607 iso