Durable and functional. These hard sided Pannier Boxes by High Country Plastic are 29" L x 14" W 18" H and are lightweight. They are available in three colors: orange, forest green, and tan (w/brown lid). These were designed with your horse in mind, with sides curved to fit your horse. Panniers are sold as a set of two. Nylon straps are 2" wide they are long enough to throw over a sawbuck, or you can shorten them to hang on a decker with decker hooks. These panniers come with screw inserts to install a set of eight metal legs (sold separately) for use as a table (table height 33 inches). Made in the USA.
Legs are available here and decker hooks are available here.