I have only run into a couple of folks that won't ship to Canada.
One guy, I finally convinced that it wasn't much more of a chore than sending an item inside the USA.
Custom declaration.
Your name and address
My name and address,
The contents of the package.
The value.
How simple is that?
I could fully understand if it involved a ton of paper work, but it doesn't.
If you are willing be pay more for shipping, you can get your item fairly quickly, maybe within a week.
If not, sometimes you are at the mercy of snail mail and customs.
I have no proof but, sometimes I believe that an item can sit in customs for a long time before it is processed.
But, it still gets to where it was sent. I have never had a shipping problem beyond the length of time it takes to arrive.
Sometimes waiting for a cue can be pure agony.