Sorry....I just mentioned the wash basins as an alternative to the large 55 gallon drums that you mentioned as unavailable. Wash basins seem to be available around the world in many sizes....usually a low-cost option....and much less work than cutting down a barrel drum. Those plastic pots you show can work. Attached is how I start out most of my American Elms....in one of those plastic pots. This Elm is much smaller than what you have...but will grow quickly as it gets established. And, because the pot is smaller I can easily move it around for the right growing condition.