Is there a link to display an app directly in iTunes U?

Although the contents of iTunesU technically aren't apps, yes.

In iTunesU, open the Catalog, locate the course and open it. In the upper right corner you will see the icon for capturing and posting a link (looks like a square with an arrow shoosh). tap that. From the menu yuocan capture the link, email the link or post to social media (depending on what you have installed or active).