You know, Sirius/Harry is one of the rare slash pairings that I am not a huge fan of for some reason, so I don't have anything off the top of my head. However, snegurochka_lee is a frequent reccer and has a Sirius/Harry (http://snegurochka-lee.livejournal.com/tag/fic%20recs%3A%20sirius%2Fharry) tag that might yield some goodies. :-)