Stewart......
Take an umbrella to put up when you stop.....this saved me in Mumbles a couple of years ago when at the lights! Got some smiles from passers by .....
As for a "cape", have a look at disability scooters for accessories. My dad had one and he used a clear cape that fitted and had a hood built in. It covered both him and handlebars and, being clear, he could see his controls. You might be able to modify one.
But.....just think of the "look"!
You might look like a condom.....
