Try as I might I can't find the current constituents of the S&P 500 Top 50 index: http://us.spindices.com/indices/equity/sp-500-top-50
That link only lists the top 10 constituents by weighting. And there is a Guggenheim fund that tracks it which lists all 50 constituents but I'd like to get the list from an official source/S&P 500.