FabFilter Pro-DS and Sonnox Suppresor.  Overall, I (slightly) prefer Suppressor's interface and worklow.  I work with multiple vocalists and I find that, depending on the vocalist or recording, one of those two typically gives me better/more transparent results than the other.

clip envelopes.

The de-esser in the "VX-64 Vocal Strip" works well and you probably already have it..

Another way to do it is to use the multiband compressor. Set the frequency of the highest band to about  3kHz and start with  a ratio of 3:1.  Bypass all the other bands.
Set threshold so the esses are getting compressed as indicated on the meter. Use your ears to adjust how much the esses are getting compressed. You can solo the high band to fine tune the frequency.