Judge - I am another who gets very little sleep if there is any light.
Here is my solution, hope it helps. At office supply or art/craft supply shops they sell a product called foam-core. It is extremely lightweight but blocks out light. It is inexpensive and can be cut with a pocketknife and a straightedge. It will not need to touch the glass to keep out the light if you measure and cut precisely.
If you take a look at my old kitchen window in the pic I posted yesterday you will see it blocking the morning sun. I use them like shoji screens. They are clean, work just right, and easy-peezy.