What Bill suggests is what you want to use but it probably isn't something that you will get in a hurry or cheaply. What I would do is check your local irrigation supply house. They use something similar for their valves. They don't have a bottom which is good because you don't want them filling with water. Set them on a couple of inches of gravel. If you can't get the depth, build up some courses of concrete brick and mortar on the bottom of the hole then set your box on top so the top is flush with the ground.
Arrange you conduit so you pull straight through. No splices.
-Hal
