Here's what I did to secure my Take-A-Look mirror:

• I cut a plastic card (discontinued grocery store discount card) to fit a niche in the styrofoam padding inside my helmet.
• Zip tied the mirror stem clip to the card.
• Zip tied the card in two places inside the helmet.

Very secure, provides just enough adjustment to tilt the stem up and down as needed. So far it's held through my one crash since using the mirror (held up better than my ribs, which are still healing). And I've snagged the mirror several times without losing it.

Only thing left to do is pad the edges and rounded corner of the mirror itself. I'm not entirely comfortable with that hard-edged mirror so close to my eyes. I'm not sure whether foam taped to the back would work. I've also considered that liquid dipping rubber.