Illinois resurces:
St Charles:
RW Display (website)
(sells new gondola and used carts...?)
Des Plaines
Specialty Store Services (website)
(new gondola only)
Elk Grove Village:
DGS Retail (website)
(new/custom gondola only)
(many gondola accessories, tho!)
Illinois retailers shouldn't have problems finding used gondola.
Chicago is a busting city, with plently of activity. This means there will be stores closing on a pretty steady basis.
I listed a couple Illinois dealers below, and there's more in Michigan and Milwaukee and Minneapolis.
You can check craigslist (website) for store fixture liquidations or used retail shelving.
A great benefit for Chicago, though, is it's just across the lake from Michigan. Michigan has some very avtive used Lozier and Madix shelving dealers, and Illinois stores are in a great position to take advantage of them.
There are several store fixture liquidators based in Michigan, so shipping to Chicago is a great deal. Shipping lanes flow through these locations, and purchasing across the lake might be cheaper than your local dealer. Any advantages Chicago gets will hold true for the nearby areas and cities, like Rockford, Elgin, Aurora and Joliet IL. If the shipping lane avoids Chicago traffic, you might even get a better deal, but it likely to be about the same. It will be a random event for a fluctuation is delivery costs to other, further from the bustle, Illinois cities. Springfield IL is a little further, but that won't affect shipping costs much, and you will also be able to draw from St. Louis' gondola dealers and liquidation sales.
When you search for used shelves, always look within your city for a closing grocery store or C store, going and tearing down the shelves yourself will usually fetch the best price. Failing that, make a few phone calls, and anyone in Illinois can some of the best shelving deals in the nation.
