Looking for a source of surplus or used 18650 batteries in Canada?

Well I fell down a youtube rabbit hole last night about building DIY powerwalls. It looks like a fun project for the winter months. I can find brand new batteries no problem, but it would appear the best way is to find used ones or surplus items. Fascinating and depressing the waste out there.  If anyone can save me hours of prowling the internet and can point out some Canadian sources it would be greatly appreciated.

Regards
Brayden

Laptop batteries and cordless tool batteries are the prime sources. Usually, only one cell fails prematurely and the others are salvageable.

I have been doing this for years; one cell powers a LED lamp perfectly, and direct charges from a 15W solar panel, if you monitor the voltage and disconnect at 4.2VDC (it's been a while) or pop! and your cell is dead.

There are always ads on Kijiji looking for these as freebies, so you have competition. But the source is massive; it's just a matter of tapping into a network.

Also, hook up with Freecycle sites. Volunteer at your local thrift shop.

The third -- and trickest -- source is municipal recycling depots. They have become very strict when it comes to scavenging electronics -- both for liability and privacy purposes. So, you're going to have to go James Bond/Mission Impossible on this (let the theme song run through your head; it helps).

Fourth, hook up with a not-for-profit that takes discarded corporate laptops and repurposes them for low income folks. The batts are usually toast; if you can build trust, there's and endless supply chain, and you do something good in the process.

Matching up cells to prevent overheating when charging is a very delicate business. I assume you are well aware that you are constructing one of the most effective firestarters on Earth, if anything goes wrong? Respect it like a big container of gasoline with a built-in ignition system and you will be fine.