Hi fellow Canadian
You can easily get Ivermectin here. Bought the liquid stuff for horses, you can get a ‘single dose’ syringe (single dose for a horse at 15ml).
This:
https://greenhawk.com/collections/dewormers/products/avl-ivermectin-liquid-dewormer-15-ml
I actually emptied the 15ml into a small jar and use a small 1ml syringe to measure out the dose.
FYI this product is 10mg/ml
You can also get 5mg/ml in ivermectin with other brands.
Here is a good article on ivermectin use in poultry along with dosing - remember there are 10mg/ml and 5mg/ml strengths so whatever you use make sure you check this.
https://bitchinchickens.com/2019/04/29/ivermectin-for-parasite-control/
It’s very hard to get stuff here in Canada for sure, but not impossible.