The HTML-Box-Widget works fine, but there is no possibility to select, on which pages the output should be.
After the installation, you find an extra widget. Pull it to the widget area you like, add the optional title and the content and you are finished.
To show or hide the content on selected pages, insert the page IDs in the correspondent field. You can use the plugin “WP Show IDs” for quicker finding the ID.
Supports HTML and Text, multiple use in the same widget area also.