From an alert reader! :)

If you go to Old Navy today in costume they will give you a free t-shirt. Pretty easy! Plus, if you go to the one by Oakview Mall, then you can just hop on over to Hy-Vee for their trick-or-treat day. I was just there and there were plenty of kids in costumes gathering treats from all over the store! (You'll need to go there anyway for their cheap orange juice!)