Chicago tofu dog
Chicago Diner has one on their kid's menu but I'm sure I've seen them on the regular/adult menu. http://veggiediner.com/index.html
Soul Vegetarian doesn't have a menu online, but they may have one.
205 E 75th St, Chicago, IL 60619
Comiskey Park has them.
Veggie Bite - http://veggiebite.net/ - is an all vegetarian (vegan actually) fast food place and they're on the menu.