The Fluky’s sight does sell condiment packs that include that unique Chicago relish, known there as picallili. Here is one such pack they offer:
This package includes 3-8oz Jars of Fluky’s Condiments. Choose from the Hot Dog Stand Mustard, the "Fluky’s Blend" Flourescent Green Sweet Relish and the Serrano Peppers.
As a Chicagoan myself, I really miss that green stuff, as well as the soft-steamed poppy seed buns (not to mention the Vienna all-beef franks).