I've been buying eggs from Country Cottage Farm via the Green City market. I'd estimate that 2/3 of their jumbo eggs are double yokes. They are also incredibly fresh, great tasting eggs.
They aren't in the NW Burbs. In fact, their farm is in Fisher, IL, near Champaign. Their website lists a PO Box in Warrenville and they seem to have other drop off locations. If you don't find anything more convenient, you might give them a call.
http://www.countrycottagefarm.com/