I'm located in Nova Scotia and I try to buy wherever I can get something cheapest (and legally). Often that means I have to order from the US and often even with shipping and duty, it can be cheaper than buying here in Canada. We live with this all the time.
First off, I bought my battery charger (http://www.paulsfinest.com/Maha-PowerEx-C801D-8-bank-NiMH-NiCAD-AA-AAA-charger-8-x-AA-2700mAh-PowerEX-Batteries-1-x-BH8-case.html
) and a lot of my batteries over the years from Paul's Finest (http://www.paulsfinest.com/
). I've had this charger for years, it is highly recommended and rated online, and the only time I had a problem (the power brick went bad probably 6 years ago), Paul helped me sort it out with the manufacturer.
I recently received an order of Eneloop AA and AAA batteries as recommended by Steven Harris, from Costco Canada. I placed the order online and it was shipped right to my doorstep.
I have a bunch of stuff from Canadian Tire (yes I have that Canadian Male dominant gene). My car and my garage/house backup power packs came from Canadian Tire - both on sale at 40% or 50% off. The garage unit is kept topped up by two Canadian Tire branded solar cells I picked up off of Kijiji locally. I also have a couple of DC to AC inverters (a couple of car units plus one larger one - I bought it after Steve Harris' podcast on back up power. Just wait for a sale and buy one (or 2).
My back up water breakers came from Walmart. I had to drive to Antigonish to get them since there were none of the ones I wanted in Halifax but I was in Antigonish anyway.
For personal hiking/camping/prepping equipment, I favour MEC. There is a local store here so I don't need to get it shipped to me. Or else I just buy it from Canadian Tire.
Here's my best suggestion, if you are ordering something from the US, make sure they'll ship it by USPS. Avoid the couriers (UPS, Purolator, etc) because they charge an arm and a leg for cross border brokerage fees. I once paid $0.45 HST on an order that cost less than $10.00 and the courier topped that up with a $55.00 brokerage fee.
Some of the couriers include brokerage fees in certain levels of their shipping. It can be difficult to figure out which level of service so I typically only deal with sellers who will ship by USPS. USPS hands the package over to Canada Post who will deliver to my door and will only charge $8.00 (it used to be $5.00 but it went up lately) brokerage fee (plus HST and duties if appropriate).
I would love to have access to everything that is available on Amazon.com but that's not going to happen up here in Canada We have Amazon.ca which will let you try to order everything you find and then only when you're trying to pay for your order, tell you that item can't be shipped to Canada.
Somethings cannot be legally exported out of the US with the proper paperwork (think gun parts, ammunition, reloading components). Some US vendors cannot export non-controlled items due to agreements with their distributors or manufacturers. Sometimes the only thing we can do is hold our nose and spend more money than we want on something locally because that is the only way we can get our hands on it (think Leupold scopes).
Just some random thoughts.
Best of luck