Anybody Know a Method to Frost a Cup With Ice?

Thinking about a "homemade root beer + sirloin burgers + Belgian fries" concept. I'd like a way to serve the root beer in a cup (disposable obviously) covered with frost, for aesthetic appeal. Those of you who are old like me remember when they served it in frosted glass mugs--like that.
 
Has anybody seen a device that can frost a plastic cup? I was daydreaming something that might blow a stream of air through a bed of dry ice and into the interior of the cup while simultaneously misting the outside of the cup with water vapor, until a good thick coat of frost forms. But somebody has probably invented something that works?
 
Ken
Tamale Trolley Food Truck
Memphis TN