[dsraven]

you could easily make them by cutting one side off a piece of square or rectangular tubing with the wall thickness desired and then drilling a hole. most metal supply places will cut the size you want for a small fee. if you wanted 6 pieces of the same size you could probably order, pay and pick up at an agreed upon time. they will want payment to ensure their cost is covered in the off chance you don't come back. they may also be able to drill the holes as well, or form the shape with flat stock, it all depends on how much you want to spend. square tubing will have the radius on the corners much like the pic shown.