If they don't fix under warranty if any, use a 2 part epoxy- one tube is glue, the other hardener, mix with a toothpick and apply with a toothpick. If you need, I have some from previous projects. I wouldn't worry about causing any damage either, cosmetics are the only concern if you're messy putting it back on. Manufactures build hype around tampering with helmets for liability reasons only; there's no real practical concern of harm with what you're doing.