I don't recall seeing the treasury editions anywhere except for either B. Dalton or Walden Books, in shopping malls. Those might have been west coast stores, not sure. They were basically my go to for any kind of comic book related stuff that you couldn't find on the spinners.
The biggest problem with the treasury editions was that if you spent your hard-earned allowance on them, it could not be hidden from mom and dad. And they would almost always give me an earful if they caught me buying funny books, especially big extravagant looking ones like one of those biggies!