The IDLE icons are from https://bugs.python.org/issue1490384
Created by Andrew Clover.
The original sources are available from Andrew's website:
https://www.doxdesk.com/software/py/pyicons.html
Various different formats and sizes are available at this GitHub Pull Request:
https://github.com/python/cpython/pull/17473
The idle.ico file was created with ImageMagick:
$ convert idle_16.png idle_32.png idle_48.png idle_256.png idle.ico