Viscosity? To me they are so close I can't tell the difference.
Here is an idea. I have a shooting forum friend that lives in Canada. His sister lives in NY state. If I want to mail him something I send it to his sister's NY address and the next time he visits her he pics it up.
Do you have any friends or relatives in the US? If so perhaps they could get you the Tri-Flow and get it to you. Like I said, just an idea.
My Tri-Flow oil bottles don't leak. I keep them capped tightly and they are fine.
Singer grease or lube is the old standard. There is nothing wrong with it other than it tends to fling off of gears. It's what you need for Singer motors though.
Have you contacted Singer for a source of their products in Canada?
Joe