We're having trouble finding a large interior planter. We're planning to grow shade-tolerant bamboo at the base of our staircase, to grow up through the open stairwell towards the natural light from our solatube. We're looking for a tall (about 30"), rectangular planter, approximately 18" wide x 24" long. If anyone knows where we can find one in the Toronto area, or has an idea of something we can construct (we're relatively handy), that would be much appreciated. The standard planters we've found seem to be limited to 16" x 16".