The tag cloud is a real widget. It is in the available widgets section at appearance > themes. What is missing is a "random post" widget, which is actually unique to this theme. There is at least one other theme that has a unique widget, but I can't remember which theme it is.
The following code, when put into a text widget, produces a link to a random post from your blog if that would help you in any way. It doesn't display the title of the post, but will pull up a random post. If this would work for you, you could then add a text widget to the north sidebar, which would make the theme's random post and tag cloud widget disappear and then your "homemade" random post widget would appear there.
<a href="http://theworldisquiethere101.wordpress.com/?random" title="Click here for random post">Feeling lucky??? Click here for a random post</a>