Adding an external link to one of the virtuemart categories

[inpixelated!]

We would like to link one of the child categories to an external website.  Another reputable company has agreed to put certain products on their site with the agreement that these would be accessible for purchase through their site. 
This category is fed through a 3rd party drop down menu module.  Should this be done in the virtuemart templates or in the 3rd party module code?  I found a solution for the previous virtuemart version but it doesn't quite relate since the file tree is set up differently in the new release.  Also, we are not using the default Virtuemart template.
Here  is the link to the original question/answer in the forum: https://forum.virtuemart.net/index.php?topic=70400.0
Here is our current J! version: 2.5.9
Virtuemart version: 2.0.14
I'd be happy to provide any other info that would be helpful.

[jenkinhill]

Before doing anything you are advised to update your insecure Joomla/VM versions - test on a backup first as you are using template overrides.
http://forum.virtuemart.net/index.php?topic=118683.0

You could use a template override for the 3rd party products category with the products all linking to the associate site.