I made mine with cast acrylic, cut the sheets, drilled and countersunk the screw holes, used tempered glass for my window, and added a quick-release tripod mount hacked off a tripod. The window was sandwiched between two layers of plastic, the inner layer having been routed out to make a beveled edge for the glass to fit in. All joints received a bead of RTV silicon (clear) and then screwed together. The rear door used compression hinges like a tool box, with a silicone gasket seal.
It worked great but I finally graduated to using bullet cameras with a solid state DVR this year. Now I get two angles and less hassle.
