The Jack Reacher books always have a strong female character somewhere. OK the books are about him so the women are not the main characters, but there are army women, musicians, lawyers, police officers and others - who are single, independent, clever and strong. They hook up with Reacher but don't want more.
Also David Baldacci - King and Maxwell for example (Michelle), and Alex in the Memory Man series and Atlee Pine/ Mercy in The road to Mercy series.
There are loads ...