Hi Kally. You can buy clear shoe boxes with lids from Dollar Tree. You can see which shoes are in the box and they stack nicely too.
Kally, you have hit the jackpot for organizing shoes in hometalk! If you click on "explore projects" then "organize" and type "shoes" into the search box and hit enter you will find a good number of them. I have chosen one for you:
I have some narrow fixed shelves in my rental closet. I found if I heel toe shoes and lay them on their side they fit in the small space. Not all pairs fit (sneakers, etc.) but there are a substantial number that do. I have no idea what the "designer" was thinking when they put shelves so close together. Making the best of an odd situation. Good luck!