My riding buddy carries a soft cloth soaked in a windshield cleaner inside a zip lock bag. He also carries a dry soft cloth. When we stop to fuel up we use them to clean the windshields and our helmet visors. It works really well.
I carry a large trash bag and use it to lay over my seat when parking overnight. Keeps the seat dry from rain and morning dew. Nothing worst then starting the day with a wet tush.

Other stuff I find in my bags:

Wire ties (ya never know)
many bungie cords
couple pair of sunglasses ( I leave them everywhere)
A dark and clear shield for helmet
tire gauge
A kickstand pad ( 3-4" round plexiglass pad I put under the kickstand if parking on stone, grass, or soft macadam)

Safe and happy travels