Reddit mentions of Copper 101-H04 Round Tubing, ASTM F68, 4" OD, 3" ID, 0.50 " Wall, 12" Length

There are plenty of places online, but it's going to be expensive.

First thing you want to make sure of is that you get the right copper alloy. Basically this means C101 to C110 copper. This is 99.9% pure copper for electrical / electronic manufacturing, oxygen free. Any of these grades will do. C101 will be the most expensive, at 99.99% purity, but the difference so far as your application is concerned is trivial.

Copper itself isn't expensive, but these grades of copper are. Moreover, the real reason for the high price is that thick walled tubing is rare; it doesn't have many applications. Thinner walled tubing is widely used for water pipes, air conditioning, refrigeration, etc. so is substantially cheaper.

The downside is that the magnet will fall faster through a thin walled tube. If you want to see a strong Lenz effect with slow fall, you need thicker tubes.

If you do a quick search on Google for thick walled copper tubes, you'll come up with a bunch of hits. Among the cheaper prices I could find is this from Amazon for C101 copper - 6.5" outer diameter, 5.5" inner diameter, 0.5" thick walls, 12" length.

It's hard to tell the dimensions of the tube in the video, because there is no scale of reference other than the guy's hand, and that's a pretty rough guide because you don't know how big his hand is. However, my guess is 5" outer diameter, half inch thick wall, 6" length. This tube I linked above has the same wall thickness, but is wider (6.5"), and twice as long. It costs $576.65 with free shipping. Conceivably, you could find someone else interested and split the cost. If you cut the tube in half, each half would still end up bigger and nicer than the one in the video, and each of you would only pay half the cost.

Or you could just keep the whole tube. 12" is a longer distance to fall than 6", so it would take a nice long time for the magnet to drop through, and you would find it easier if you wanted to flip it upside down when the magnet reached the bottom, and prolong the effect.

Keep in mind that this is a hell of a lot of copper. That tube I linked would weigh over 16.5 kilos, or almost 37 pounds. If you want something lighter and cheaper, there's this tube which is 4" outer diameter and 3" inner diameter, but still the same half inch thickness. It sells for $347.53, but again it's 12" so you could cut it in half and split the cost with a friend. It's still over 21 pounds of very pretty copper.

For the magnet, you need a neodymium magnet. These magnets are extremely powerful (and expensive) and dangerous when in large sizes like the one shown in the video. They come in grades, usually labeled like "N32" or "N42" or "N48". The higher the number, the stronger the magnetism of the material, but don't be fooled by low numbers. If the magnet is big, it is dangerous even if it's relatively "low" grade.

By "big" I mean a 2" disk that's at least an inch thick, like shown in the video. A magnet that size can break your fingers, shatter the bone like it were candy cane. You don't just pull the magnet out of your drawer to play with it, absent minded like. You store it carefully, you plan ahead of time how you'll bring it out, you prepare a work surface in advance where you'll be handling it. Like in the video, the guy had a large wooden surface to work on. You don't want it coming near any ferromagnetic material, specially large chunks of it. A big magnet can have a pull measured in the hundreds or thousands of pounds. It's beyond the capacity of an average sized man to pull it off, you need leverage. And they are brittle. If they come in contact with something suddenly, they will shatter into tiny bits. Wear eye protection.

Here's a magnet off eBay that will work with either tube listed above. It's a 2" disk that's also 2" thick, making it pretty damn powerful. The material is N48 and it's $160. You can shop around and maybe find a cheaper deal. There are a lot of neodymium magnet sellers on eBay. I've bought from there before a few times and never had problems. Just look for the seller's reliability rating and the magnet's grade/size. No need to worry about anything else, there are no other differences. They're all churned out the same few factories in China.

Like I said, it's an expensive hobby. If you just want to see the Lenz effect, you can buy much smaller magnets and thin copper tube for $20-$30 bucks combined. But if you want thick copper and big magnets, be prepared to pay.

Again, be careful around big neodymium magnets. Pinched/bruised fingertips are quite normal, and shattered fingers and broken bones can happen more often than you might think. All it takes is a few second of carelessness. Good luck.

EDIT: never mind the dogecoin, I don't want it.