b) Add a sidebar area to your child theme by creating a functions.php file in your child theme and registering a new sidebar. (Like style.css files, child theme functions.php files do not overwrite the parent theme’s functions, they add to them.)
c) Add the sidebar to the necessary template files (index.php, single.php, etc) in your child theme.
d) Style the sidebar display with css and you’re done!
I swear it’s less work than it seems. 🙂 And it will be much more reliable across different browser types. But if someone wants to chime in with a rock solid css solution, I’d hear that, too. You would still need to create a child theme or use a custom css plugin, though.