Extra Large Galvanised Tubs
These enormous planters from Turkey would work well indoors or out. They are certainly big enough to cope with a small tree and would look fabulous with an olive or citrus in them.
I recommend lining them with some kind of insulation if you are planning to position them in our harsh New Zealand sun as the metal can overheat the roots of your plant. Something like some old polystyrene sheets, wool, or bubble wrap would do.
approx 60cm wide at widest point
approx 30cm high