Thanks! You can order from Digikey and Newark/Farnell without the extension though it's still a little bit better with it (less steps for Digikey and references are added for Newark/Farnell).

The extension source code is available at: https://github.com/monostable/1clickBOM and it's been extensively reviewed by Mozilla for getting it up on addons.mozilla.org.

(Source code for Kitspace is on https://github.com/monostable/kitspace by the way.)