Chrome extension downloader in JavaScript. It just extracts the extension id and builds the download url for you.
If it doesn't work, try with this URL. Replace ~~~ with the extension id.
https://clients2.google.com/service/update2/crx?response=redirect&os=linux&arch=x64&os_arch=x86_64&nacl_arch=x86-64&prod=chromium&prodchannel=unknown&prodversion=91.0.4442.4&lang=en-US&acceptformat=crx2,crx3&x=id%3D~~~%26installsource%3Dondemand%26uc
Alternatives:
Last update on: 2022-04-28
This sets the destination filename in the command below, so you can download updates for an extension without overwriting old versions.