Have you simply considered using the noindex manager for the category page (to prevent the duplicate content from getting indexed) as an alternative using the Meta Robot Tags Editor?
If so, then simply change the global rules using Meta Robot Tags Editor >>> Default Values >>> where you can prevent indexing of:
Administration back-end pages
Blog search pages
Subpages of the homepage
User login/registration pages
or, for fine-grained control, you can select the Meta Robot Tags Editor >>> Categories >>> then choose nofollow to the one in question instead of worrying about a canonical issue.