Black Out Stuff for Windows - Stop Sun Coming in

I need help with blocking out the sun.

Bought curtains, had then fitted all with black out material...which is great and does work. Except the light peeps in from the top and the sides and in one room slightly at the bottom.

Was thinking of just getting a long piece of material and draping over the top and down the sides....but would this have to be blockout fabric too?

Where can I buy just the block out stuff from?

Or how can I secure the curtain to the side of the window / wall without ruining either?

Is there something you can stick on the windows at all?

Help, I need complete darkness in my little girls room or late nights and early mornings with the sun beaming in are going to be a nightmare