i looked online for a large azalea pot, because I will need one soon for an L anceps that is outgrowing a 12" tree fern pot. I found a couple of distributors / mfrs that sell 15" azalea pots; not sure if they will sell just one. But, they exist, so a garden store might be able to special order one for you if you can't scrounge one up online.
That plant looks great now, how cool will it be in one or two more cycles? Amazing.