My friends really wants to get a guinea pig, but I'm urging them not to buy one from one of the big chains like Petco, because I feel those chain pet stores aren't very good at keeping animals healthy, and I don't want them to wind up buying a sick one.

Do you know of any reputable dealers in the SF Bay Area which specialize in guinea pigs and can be trusted to sell my friends a guinea that's been properly cared for and is in good health?

Thanks!