If you're doing it because of the micro bubbles just get a foam filter pad, like the ones that they sell for the Whisper filters, and cut a slit in the middle of it. Then slide it around the lip on the return spout. That should remove most of the bubbles.
Thanks all, yes I need one for Maxi-jet 1200 powerhead. Purpose is not bubble issue, but I have sumpless setup and the surface skimming would Really help. I found DIY where guy using PVC into mag powerhead to skim, not sure if that'll work for MJ1200.