These shops always have a decent selection of singles.
The must sees:
-Eastridge (they have a clearance box and their showcase singles are incredibly competitively priced)
-Maple Leaf (previous times I have been there, they have usually have a decent assortment of singles)
The if-you-have-time-to-visit ones:
-Andy's Sports Cards (smaller shop with a good mix of singles and product)
-Collector's Books and Cards (you just have to ask them to see the cards in the piles/boxes in the display cases)
The you-can-pass-by-them/only if you wanna see all of the stores in Calgary ones:
Celly Sports and Games
Olympic Sports Cards and Games
Overtime Sports Cards and Grading
If you are able to do the short drive to Airdrie, I also highly recommend Morrison's Trading Post. Great selection of singles and the most comfortable singles box browsing space out there in the hobby. And you feel super welcome and unpressured while shopping there.