I have a little box for my tooth brush and paste that might work. It has a divider down the middle that can be cut out. I havent got it with me so cant measure it, but it will take a medium large tube of tooth paste, and easily fits the long tooth brushes.
I wouldnt call it waterproof, but I have used one up a mast wrapped in gaffer tape to weather proof a small amp and diplexer for a tv antenna. It kept most of the weather out.