So, find the required logos online or somewhere, scan and make the design(s) you want. Go to a commercial printer, promotional materials supplier or vinyl sign maker and have them make them. Stick them to the back of a piece of clear acrylic/perspex/lexan to get the illusion of depth and some gloss. Speak to the commercial manufacturers of custom advertising signage I mentioned above. They'll tell you how to do it, 'cos it's what they do for a crust. I have no idea what it'll cost.
If you want to get fancy get a piece of wood and router out a channel in it the same thickness as the acrylic and quite deep, mayke an inch or so. Run a set of those low voltage lights in a tube along the channel, then insert the acrylic in and glue or screw. The light will stay mainly within the plastic sheet and light the image glued to the back.
Personally it's not to my taste, but.......even still......it's always better if you roll your own.
I would think for the most part you could only get these signs if your theater has been certified for these diffrent formats. That doesn't mean you might not be able to scrounge something up that a theater is throwing away. But I wouldn't think that there is any place to just order something like that. The post above mine sounded like a great idea.
I know you can get them. There is a place that sells them along with other home theatre decor stuff, such as poster light boxes, theatre style seats and popcorn machines. I don't have the name of the place on me, but I'll look it up when I get home.