Privacy Search от David L.

Whatever your browser's search engine options are, this extension intercept request to Bing, Google and Yahoo and redirects you to a privacy aware search engine as DuckDuckGo, Framabee, Oscobo, Qwant or Startpage.

Qwant is used by default, but you change select the one you prefer in extension's options.

Icon made by prettycons from Flaticon under CC 3.0 BY licence :
https://www.flaticon.com/authors/prettycons
http://creativecommons.org/licenses/by/3.0