My take on the original series PADD. I based it on measurements of the original that have floated around the Internet and averaged them out. The holes are sized to fit Osram/Sylvania 662D lamp holders like the original. You can still find these online. The most common lens colors for the prop are, left to right, red, white, orange/amber.

Yes. It requires a big print bed, so I've included a 2-piece split version.

The loose pylon is meant to be glued in near the switch and the left light to provide stability and reduce flexing when the switch is pushed. I left it loose as you may want to move it depending on your electronics or what you use for the screen (the original used a Magic Slate toy.)

As for the back, you'll need to cut a sheet of something for the back. Printing a sheet of plastic seemed a bit pointless. I'm using a sheet of 12"x12" ABS, but Kydex, or other hobby plastic (or wood, for that matter) should work for you. The dimensions for the back are 210m x 265mm x 4mm. The blocks in the frame provide stability and a place to screw the back to.