I'm not familiar with shops in that area, but a professional hitch shop would be my first choice. Most medium-large cities have them. There is a place called Master Hitch in Palatine that sounds promising:
http://www.masterhitchpalatine.com/
U-Haul dealers can sometimes be a good choice, but some are real pros while others not so much, so look them over carefully before trusting your Z to them.