Two places one a bit closer than the other.
The closer is in a town called Niles and it's an REI store at
8225 Golf Rd. (Four Flaggs Shopping Center) (847) 470-9090 They have a website at www.rei.com so you can see what them might have. They carry more items on their website than in the stores.
The second is Offshore Marine in Vernon Hills at a shopping center at the ntersection of Rt 60 and Milwaukee, (River Tree Ct Store #348 Vernon Hills, IL 847/362-4880). They too have a website at www.offshore-chicago.com. Their hours are quite a bit shorter than REI but they have much more kayak specific gear.

Mitch