Redirect to user activity page when clicking seller link

I'm wondering if you could help me out with a bit of coding to handle a redirect.

In Classifieds, with BuddyPress, when someone clicks on the seller's name, they are taken to the seller's Classified's tab on the user profile. I have a slightly different than default setup and would like to redirect the visitor to the seller's BP activity page instead so that they can post a message to the seller in the seller's activity stream. I'm not using BP private messaging on this site.

I'm aware that Classifieds has a built in email contact form, but it is not appropriate for the environment for this site (a corporate intranet).

I suppose what I really need is a just a function that I can drop into functions.php to handle to redirect from the classified's tab of the user profile to the activity tab of the user profile.

So that this on the classified ad page:
http://example.com/staff-members/username/classifieds
redirects to this:
http://example.com/staff-members/username/activity
or this, since I have activity as the default BP tab:
http://example.com/staff-members/username/