Hmmm.... This is indeed an interesting concept. As a microbiologist, I know that there a different sizes of petri dishes. There are really big ones, normal size ones, and small ones. I'd be lying to say I know the dimensions off the top of my head, but the small dishes would be perfect. The samples would have to be very secured for transit as the plastic petri dishes can crack. This is a fantastic idea. I like the ease of creams, but there is something about lathering from a soap.
"Better to keep your mouth closed and appear a fool, then to open it and remove all doubt." --Mark Twain