32x23x9 inches, that is one large pot. Not many bonsai pot makers in the USA have personal kilns large enough to fire the pot. Would likely have to find a potter who belongs to a co-op where a group uses a large wood fired community kiln. It can be done, there are a number of these kilns near most cities where you have ceramics artists making ''stuff'' that is not bonsai related. Unglazed clay picks up an interesting finish in a wood fired kiln.
I'd list potters that do slab build larger pots, but I'm afraid I would skip one of the better ones, there are at least half a dozen in the USA.