You can do the same thing with SingleFileZ [1] which can protect saved pages with a password. It relies on the zip specification to store the encrypted resources (html, images, css, etc.).

Here's an example of protected page saved with SingleFileZ: https://gildas-lormeau.github.io/private/ (password: thisisapage)

[1] https://github.com/gildas-lormeau/SingleFileZ