I do not know of any pop stores like you describe in the Chicago area. The only one I know of is no If's Ands or Butts in Dallas, which has been previously discussed.
In terms of Dr. Pepper, I went to the Dublin, TX bottling plant, where they still make Dr. Pepper with cans sugar and picked up a case last summer. Let me tell you that there really is a difference! I'm not really a Dr. Pepper drinker as a rule, but that stuff rocks! I also had some of the best BBQ in that part of Texas on the way back to Dallas. It was served from a little side of the road BBQ shack. I'd go back again just for the BBQ, let alone the Dr. Pepper.
You can read all about Dublin Dr. Pepper
here.
Steve Z.
“Only the pure in heart can make a good soup.”
― Ludwig van Beethoven