Jeri Jennings recommends these to foil gophers when planting roses in the ground (with lots of extra holes drilled for drainage). I prefer cages plus trapping myself, but I do use them for planting blueberries. My soil here is quite alkaline, and planing in pots makes it easier for me to control pH.
Anyway, I've had an awful time finding them. They can be ordered, but the only time I found them in a store I had to drive 50 miles to pick them up. Well, today I was in our local CVS drugstore and in the garden center at the entrance, I found a shelf of nursery pots and they had 15 gallon squats!
I bought nine, which was about half of what they had. The price was just under $10 each. They looked quite sturdy. If you have been looking for these pots with no success, you might be able to find them at your local CVS right now.