"Geez, you really are a Slytherin, aren't you? So suspicious," George laughed, rummaging around in his bag some more. Where the hell were those bloody stones?
"You seem like a nice girl, Astoria. You're sister's a nice girl too, though she manages to hide it very well under layers of disdain and horrid shrieking noises. And I just happen to be the type of person who doesn't like to see nice girls be miserable. Aha!" he finally caught hold of a set of two green crystals which he promptly pulled out and held out to her.
"What about these, then? They're only a prototype; we're not actually selling them yet. I could use someone to test them out for me... See, they have a set of invisibility spells on them that makes the person visible only to the person who's holding the matching crystal. Perfect for secret meetings, romantic rendezvous... You don't know anyone who could use anything like that, do you?"