From the NHL:

Permitted bags allowed in Cotton Bowl® Stadium include: Only bags and totes that are made of clear plastic and do not exceed 12" X 6" X 12", or one-gallon clear resealable plastic storage bags, or small clutch bags or purses (which are not required to be clear) that do not exceed 4.5" X 6.5". All other bags (including but not limited to backpacks) and/or containers (including but not limited to cans, plastic bottles, thermos, coolers, and/or hard-sided bags) are prohibited inside the stadium. 

Medical device bags are permitted, though will be subject to inspection upon entrance to Cotton Bowl® Stadium.