Waving to you from Ontario, though I grew up on Van Isle.
There is no dry food, prescription or otherwise, in Canada that is low enough in carbs for a diabetic cat.
A number of Canucks feed Fancy Feast
pate (called "classic" in the US) and Friskies
pates. Some people feed their cats a balanced raw diet.
You can find a ton of information here:
http://www.felinediabetes.com/FDMB/threads/index-health-links-faqs.194624/
Scroll down to the food lists.
Note: the Canadian chart contains available-in-Canada only foods and may be a bit out-of-date.
Before attempting a diet switch to low carb, you must be testing regularly – before each shot and at least once during the cycle. Switching to low carb can drop a cat's number by up to 6 in world numbers (that's 108US – multiply by 18 to get US numbers which are the norm here but most of us can read both).
And do familiarize yourself with what to do in case of a hypoglycemic event. ("karo" in Canada is corn syrup – honey, maple syrup will do just fine as well)
If you encounter lower numbers than you are used to, please start a new post and someone will stay with you to help getting the numbers up to an acceptable level and keeping them there.
There are better insulins than Caninsulin for your cat. Lantus is a good choice, and very inexpensive in Canada. Lantus is having some supply issues due to the virus. Basilgar works very similar to Lantus.
I don't want to overwhelm you with a ton of information. Ask questions. We like questions.