I have been trying to find some 40 gal plastic nursery pots for the longest time. A gentleman at the Broward Rare Fruit Council fall plant sale told me that landscapers throw the used pots out when they are done with them.
I saw the landscapers that maintain my development planting some trees this morning and I asked them what they were going to do with the pots the palm trees were in, they said throw them out. So, my Sweetheart Lychee and a couple of my bigger mango trees now have new roomier digs. And for free.
So, keep your eye out for those guys on the side of the road doing new landscaping installations.