I spent two weeks (quite a few years ago) in Norway above the Arctic Circle in June, which meant sunshine 24 hours except when it rained. All of us at the hostel slept when we felt like it and were out fishing in their rowboats at midnight, followed by a 2 am fish fry. So it helps to be flexible!

I'd go with the sleep mask which is not only the lightest option but the most versatile.