Clear-coating for costume plated Writing Pen tubes

Looking for a product to protective clear-coat gold-colored costume plated brass tubes for Writing Pens. It needs to be: water clear, non-yellowing, scratch resistant, won't peel-off. Also, I need any advice available on coating these round tubes, so that the clear coating doesn't puddle-up, or pool, in one area before it dries. ALL help is appreciated!

Toika Bridges