Try Avi Shulmans book. He’s taught many many people, successfully.
I heard him once say, before he started teaching PS, he looked into it. He found that fifty percent of those who attended public speaking courses in college feel uncomfortable speaking. (Hopefully its changed since then).
Nervousness at times can contribute to a very good speech. If I dare say, do you remember any speeches from the last Siyum Hashass? The ones I remember are from the two speakers who looked very nervous.