Disney size pots.
Have you looked at Amazon? They have a good selection.
Try your local Home Depot or any Nursery
I buy mine at Dollar General! They are plastic, but still last a good long time and are very inexpensive.
Costco has giant pots too.
Home Depot has large pots but I would check with a local nursery they may be able to order some in for you or even have catalogs for you to pick from.