Wilderness Exchange is within walking distance of Union and they require you leave a bag with them when you go into the store, they may be willing to stash your bag for a few hours. No guarantee on that, but an option if you can't find anything else. They are only open 10am-6pm on Sundays, so you may have to wait around a bit or pick it up early depending on when you get there and will be leaving.
Lockers are only available to currently enrolled students and current employees. The University is not responsible for the contents of any locker. Users must use the lock provided by Roosevelt University. No stickers or posters are allowed on the lockers. No dangerous or illegal items may be stored in lockers at any time. Items causing unpleasant odors are not allowed. Lockers must be able to be fully closed at all times. Roosevelt University reserves the right to open lockers at its discretion at any time and to remove any items it believes compromises the safety or environmental quality of Roosevelt University. Roosevelt University reserves the rights to charge for damages to the locker and may cancel this rental agreement at any time for any reason.