Mayne Fairfield 11" x 48" Plastic Window Box (White) or Black for $103.20 shipped after code OUTDOOR20.  Here is a screenshot for your reference.  It is molded from high-grade polyethylene with built in UV inhibitors, and features double wall design, sub-irrigation water system, and has inside dimensions of 44 in. L x 7.5 in. W x 8 in. D and approximately 9.5 gallon soil capacity.  It also includes 4 wall mount brackets with a black powder coated finis.