This is too late since you're already at the show...
But it is a medium size duffel bag. And the stage ushers are really strict about taking things out of them during the show. One time some parents brought their son to the show, and I think he had ADHD or something, and he had a stack of papers in his hands and ruffled them around, and kept making noise during the first half of the show. The stage usher made an extremely mean face at the parents. I felt bad for the boy that his parents would put him in that position because he probably didn't know any better. Anyways, I know it really has nothing to do with the thread, but..yeah...
"We like to snark around here. Sometimes we actually talk about theater...but we try not to let that get in our way." - dramamama611