I can give you a recommendation. Check out a story called Those Who Are Left Behind by Jamelia116. It is archived on both Fanfiction.net and Archive of Our Own. It's not just about a Harry/Seven relationship, there's a lot of other stuff going on. It's a canon divergent AU that covers the first half of season 4. It was written a long time ago, when Voyager was in it's first run I think.