So I decided to make my own with a wooden pallet. Finding the pallet was the first challenge but then I just walked down the laneway behind the shops on Bloor Street and I found several at a corner market that sells produce. I asked permission before taking it and then carried it home.
The pallet was a bit danaged so I reinforced it with a few screws. Then I took off every other plank on the front and then lined it up with one of the remainig planks and screwed it into the back, forming a bottomless shelf. Then I took some of that black weed membrane you see in the garden centre (it is perforated to allow water and air to pass) and cut it to line the shelves. Then I stapled it in place with a staple gun. I put soil in the pockets and started to plant. But alas, I discovered that my pockets were very droopy because I made the pockets a bit too roomy, so they sagged below the "shelf" when full of wet soil. To remedy, I used the two additional planks and cut them into squares the same depth of each shelf and then fastened them on at the bottom (two per shelf) to give each pocket some support.
An excellent side benefit is that when you water starting at the top, all excess water filters down to the lower shelves. Economical and efficient.
Total cost of my solution: about $10 for the weed membrane and a few bucks for staples. I also bought a staple gun, but it is not really fair to place the cost of that here cuz I'm going to use it for lots of other stuff.