Biodegradable corn cups

[vehement]

Does anyone know where to get biodegradable plastic cups (made from corn) for public use? When I was at Bonnaroo I drank overpriced lemonade out of one and was impressed that it seemed substantial even though it was obviously thinner plastic and not made from the "bad stuff."

Costco? Sam's Club? Or is online my only avenue, even if the shipping is horrendous?