Mac666: A highly durable, light weight take-along-pit is a simple project to build. You simply need a small frame made of some type of angle iron which is easily bent to the desired size. Bolt a 1/4" thick piece of conveyor belt to the bottom. Cut another length of the belt about 4" high, (12" for the back board), which will be the back, sides and front. Bolt this to the angle iron. You need a 4" wide piece of flat iron, cut to your desired length, to weld the stake to. You cut a one inch hole in the center of the pit for the stake. Then add mud. I've made a few of these, usually about 24" by 18." Note the absence of wood! Of course it is much easier just to drive two stakes into the ground.

PS: Before you go on the trip, mix your perfect mud, then place it into a cooler. The mud will retain moisture and STAY perfect for days.