I just found this wonderful site to help you with your monologues: it's called Splendid Speaking and it "supports advanced learners of English who want to develop their top-level speaking skills and communication strategies."
Each week, they tackle a specific issue on how to talk better English. Take, for example, this lesson about "how to captivate your audience with memorable introductions".
They also offer you the possibility of subscribing here! "For immediate access to transcripts for current and previous Splendid Speaking podcasts, and to be alerted to new materials on the website, sign up now for our weekly newsletter."
You can also access their blog from here.