We have a motorcycle trailer that we pull behind our Goldwing. Even inside of the closed trailer, I keep our camera and other electronic items in special padded bags that we bought specially for the item as it has been know to leak in a heavy downpour.
I wouldn't consider making a bag for the expensive items if it's going to be exposed to the weather. I have yet to have "me" stay dry in the rain in special rain-gear I wouldn't want to chance our electronics. But that's just the worry wart in me.
Good luck though
