Probably Rona or Home Depot, had them for years. Canadian Tire probably has them too.
Yeah, check the plugs in your house. Depends on the age of the house but a lot of times the outlet will look like a modern 3 pin one but will show "no ground" because it was wired before 14/2 with ground was in common use. Good to know for sure if outlets near grounds or water, like kitchen outlets, are grounded or not.
I use the trailer one on unknown power sources. If its not a grounded supply I want to be aware of it. Yes, the Sons of Norway power supply is grounded