Unlike Hopper, most celebs don't want the public to know they sell products overseas (and thus won't comment for stories such as this). Even though Jodie Foster, Mariah Carey, and Sean Connery all look sexy in their ads, they are tight-lipped about the business. Says a spokesman for one poster boy, ''Everyone knows it's embarrassing to turn up in ads they wouldn't be caught dead doing here.'' Adds another industry source: ''It looks like they're selling out. But if I was being offered $1 million to do a half day's work, I'd do it too. Who wouldn't?''