The COT report from Quandl is indeed not available anymore, since NASDAQ has acquired them. All remaining Quandl data is now also behind a paywall. The best way to get the COT report is reading it directly from its original website (https://www.cftc.gov/dea/newcot/FinFutWk.txt).

Continuous futures data is usually not free, at least not in higher resolution. You can get free ES data from our download page.