SEEKING FOR THE MOST UNCOMMUN BEAUTIFULL SHELL

[jkazan]

Hi everyone, I hope you can help me. Im a screenwriter and Im looking to find a shell for my screenplay. It needs to be a shell thats really hard to find or get. Nothing commun.
Im mexican, the story takes place in mexico so It is better if the shell could be found in mexican water but it is also ok if it is not mexican. I really  need to have  a shell that is really hard to find. Or an incredibly beautifull shell.

Any ideas or suggestions will be helpfull.
Thanks on advance