I'm looking for some dressing/shopping help for an upcoming trip to the U.S.

I'm a 2X (on a good day) stand-up comic and I'm looking for some new clothes to wear when performing. I am predominately stomach, so fitted things won't work. Think Humpty-dumpty more than Rubenesque.

Ideally, the clothes should give so I can move and I should look polished. I generally wear black jeans or trousers and a longer shirt/tunic or an extra-large shirt over a shell.

Right now, I am looking for longer-length shirts or tunics.

One of my favorite tops for traveling and performing is made from an unknown synthetic material. Wrinkles fall out, machine washable. It is smooth and stretchy, has some heft, but falls and doesn't cling. Know what material that could be or where to find tops made from similar cloth?

One last thing: I have the widest foot known to man and need comfortable flat shoes that look decent with pants. Can you suggest a style that is "in" now that might work for me?

If you can offer stores/catalogues to try or other dressing suggestions in general, I'd be really grateful.

Thanks!!