I do not have to worry about it now, but back when I had a bike without bags, I had a swim wallet. It is a locking credit card sized waterproof case that you can put some cash and your room key in and take to the pool or diving. I put all my papers in it and kept it in my pocket with my keys.

 

My lay down plate holder has a secret stash tube attached to it behind the plate itself. It's water tight too.