find . -maxdepth 5 -type f -path "*sites-available/*"|xargs egrep -i openid gives me: ./server0/etc/apache2/sites-available/some.vhost.eu.conf: DocumentRoot /var/www/openIdKnp/public ./server1/etc/apache2/sites-available/different.vhost.eu.conf: OIDCRedirectURI https://bla.bla.bla.
and to compress all of the files into single tar archive:
find . -maxdepth 5 -type f -path "*sites-available/*" -exec tar -rvf /tmp/out.tar {} \;