I bought some black cloth at a crafts store and trimmed it to the size of the top of the shade. Used some small velcro tabs around the frame of the shade and on the shade itself (along the sides) to hold the cloth in place. You can access it from the top by keeping the shade closed and opening the sunroof. From inside the car, it looks fine and the shade doesn't let any light through. It generally works OK (so long as you don't open and close the shade too much - sometimes a car wash messes it up a bit), and I usually take it out in the winter. Not perfect, but I agree that it's ridiculous to not have the ability to block out all sun - for blocking both heat and actual sunlight.
