Blocking light at the top?

I can't figure a easy way to block the light at the top of my scubber? I have zip ties that wrap around my PVC pipe as I'm guessing most of you do. What does everyone use to block the light and how do you attach it to the pvc?

http://www.radio-media.com/fish/UserJdlOnAS-2.jpg

http://www.radio-media.com/fish/User...tersOnTR-1.jpg

http://www.radio-media.com/fish/UserGrAhF11onRP-1.jpg