Another rubber-grip option you might want to consider are the Pachmayr Presentation grips. These are not traditional-looking at all, but my hand has always liked them. You just need to be certain that you get the version for the Blackhawk (same as Single Six grip) and not the Super Blackhawk.
Of course, I really like the Bisley gripframe, too. But that is a whole lot more money than either a Pachmayr or Hogue aftermarket grip.
Blunderbus