OK, here is an alternate.
The problem is that the original rig had two lengths of conduit coming up into a 4x4 weather proof box that was not proof from being buried in the flower bed.
It rotted away. At least three conductors come out of one of the conduit and dive straight down the next. I don't like the idea of cutting them and trying to extend them, such that I can install a fresh box to contain the the wires in a proper box. And I doubt that I can get the connectors off the conduit and screw them into a fresh box.
So, how about this? Buy two plastic 4x4 boxes, and cut them with a bandsaw thru the two holes in the bottom, so that there would be a half deep box with two half circles, and an open faced thing with two half circles, and then clamp them over the two conduits and their connectors, with plenty of glue. Possibly some screws to hold them together.
You toss out half of what you buy, because you want to have the holes be the correct diameter, and not narrowed.
Or: cut one box in half, and use the gasket from a spare cover plate between the two halves. Silicone to stick the gasket the the back half of the box. On the back box drill out the four corner holes for fixing the face plate clearance diameter for 6-32 stainless steel screws. Run those in from the back and into the front, but don't snug it up until over the conduit connectors. Let them run long enough out the front of the box such that stainless steel nuts can lock down the cover plate?
At least I have a box, admittedly not one that has been approved as a retrofit box, but what else am I going to do?
And what the hell, drive some unistrut down behind the box to back it up, run a screw or two to tie it in. Or copper pipe.
And then a hand hold to protect the whole mess in? Keep the dirt back and the water from the sprinklers away?