They make bigger ones. They also stack and lock to each-other, very sturdy. I've went on several rides with both attached without issue. I went with the 2 smaller ones, since I don't always need the second box. The lid of the smaller ones have a removable piece of plastic to get a bit more space out of it. Links below. If there are bigger waterproof ones you know of, do share! I'd love to get more storage without riding with the empire state building on my rear rack :clapsmilie: I do wish they were about 8 inches wider.
Bigger.
One I use.
