You could install a skylight.

Call a local window tinting company that does a lot of House Tinting.

They have obscure tint that will work on double paned windows. We have done it a lot to new construction and for others who have forgotten to do that same thing.

Or you could order new sashes if its a Double Hung window.

Have you considered shades for the bathroom? Bali Blinds offers "dual shades" where you can combine solar and/or roller shades for both light control and privacy. This would give the privacy you need without making the room so dark that it's like a crypt. Top it with a pretty valence. Bali has a great website with a free mobile app for selecting swatches, a "My Decorator" tool that lets your select your wall color, floor color, furniture color, etc. with the swatch that you are considering.

If you are of my "vintage" you remember the roller shades in the public schools. These are a whole different animal. Don't be afraid of the roller shades. Check them out at www.baliblinds.com