You should try your local grocery store. They get food into the meat dept. & deli in 5 gallon buckets. Like potato salad & coleslaw. When they are done with them they just throw them away. They would love to give you as many as you want.
I even got a 5 gallon bucket that had choc frosting in it from the bakery dept.. Guess what there was enough frosting left in there to frost a cake. Although I just ate it with a spoon.
Al is right your grocery store will have food grade buckets of various sizes that work great. Nice thing about the Briner is it has the plastic piece that locks down over the top of the meat that keeps the meat fully submerged in the brine. I found a way of doing it in a regular 5 gallon food bucket. I save all my empty quart apple juice bottles. Fill them to within about 2 inches of the top with water and freeze them.
Once I put my meat in the brine bucket I put a frozen bottle of the water on top of it which holds it down in the brine as well as keeping it extra cold which is important.