You have about 20 feed stores in the Toronto area.
feed stores - Google Maps 
Get on the phone and find those that sell grit. Forget those with only dog and cat food.
Study this treatise on sour crop and learn how to prevent it.
How to avoid sour crop and a crop-bound chicken - thisNZlife 
I read about people experiencing sour crop frequently but I believe it is easily avoidable. 
I come by that belief because I've raised about 3,000 chickens in my life and never had a chicken with sour crop in all those years. 
I also have never had a chicken with a respiratory illness. That's because I place ventilation as the most important concept in housing. 
Keeping chickens isn't that hard. Don't keep them in a cave and feed them the way they would normally eat.
Chickens in the wild don't get sour crop nor have respiratory issues.