Well, if you have an iPhone or iPad and use Zoom - the Overviewer app is a great and free alternative. What I really like about this app is the ability to rotate your screen easily to landscape and zoom in and out.
Once you start Zoom and screen share you then have options at the bottom of the screen (see embedded picture below).
select the three dots for settings (see picture below)
depending on type of iPhone the far right deals with different lenses
Embedded below is a followed by a 2 minute and 7 second YouTube tutorial followed by a tutorial that the creator made (very informative and easy to follow).
Good follow as well on Twitter to stay up-to-date - https://twitter.com/OverviewerApp.