There is a website called webarchive.org which indexes old websites including download links but only if they are small. The Windows 10 Media Creation Tool Download Page has been indexed. You can download the older versions of the Windows 10 Media Creation Tool from it (I have not tested what ISO they create or if they still work).
Version 1507 (Build 10240)
Version 1511 (Build 10586)
Version 1607 (Build 14393)
Version 1703 (Build 15063)
Version 1709 (Build 16299)
Version 1803 (Build 17134)
Version 1809 (Build 17763)
