Sam's Wine and Spirits (
http://www.samswine.com/) has locations in Chicago and the sw suburbs; they are "the single leading beverage retailer in the world." I'm not sure what Spanish beers they have, but I'd at least check them out online or shoot them an email.
DiCarlo's Armanetti (
http://www.dicarlowine.com/) in Chicago and the 'burbs I'm pretty sure has Spanish beer, as well.
There's a Spanish restaurant family who owns places like Emilio's, Meson Sabika, etc, and I know they serve Spanish beer - maybe you can contact a Spanish restaurant near you and find out where you can buy the beer?