Penis trousers.
Clown Makeup.
Job's a good'un.
Best thing to remember about public speaking is that your probably not the only one that is going to be speaking, so it doesn't matter.
Also, even if you make a COMPLLEEEEETE tit of yourself, people will only remember for like, hours so no hassle. Plus, once you've finished, it's all done, and as silly as it sounds, people will only really notice you if you do make a div of yourself. So confident, clear speaking, and you will slip under the mickey-taking radar.
Best of luck mate!