Since this is a very specific hack, chances are you'll have to do it yourself. No big deal though, I added something similar to store starting/current/goal weight for my members.

1. Create a new filed for the link in your user table (mySQL)

2. Edit member.php see how they treat the home page link, and do the same for your additional link.

3. Edit the templates for edit profile, modify profile, get info, and post to include those links.

If you haven't hacked your forum before, make sure you backup everything before attempting to do this.