Names Unlimited in Ohio, is generally the preferred company to make up the aluminum door signs. Discuss with them exactly what you want, and size, because every order for signs is up to the customer.
As for the roof sign, you will need to find a sign company that still is working with translucent paints for backlit signs. They start off with a piece of clear plastic, and then they make a vinyl sign pattern with the letters cut out that is "glued" to the inside of the plastic. Then the pattern is sprayed with red translucent sign paint. Next step is to remove the pattern, and to spray the complete backside of the piece of plastic with white translucent paint. That is how they were originally done by Superior. It isn't a difficult process, but it does take time, and the paint is both lead based or non lead based, but either way it is very costly. Also, it takes a level of expertise to apply the paint evenly. I need some signs made for my 1978 Superior, and when I get to that point, I am going to have a local restoration shop the I use do them for me. He is an excellent painter that will get it right the first time.
For those reason, most sign makers will just put vinyl letters on a piece of white plastic, and say that is all that is available to do today. There is another choice, but it is also expensive, and that is to have translucent vinyl lettering applied to the white translucent plastic and call it a day. It isn't quite the same as original, and most people wouldn't know the difference, however, the material is expensive, and they would have to purchase a whole roll of red translucent vinyl which is also very expensive. That is the reason that most sign companies will use standard vinyl to make the lettering out of.
Personally, I think that the plastic signs are something that you do when you are in the final stretch of the restoration, not before. Putting the signs in and out isn't a good idea, since the screws go into fiberglass, and each time you remove and replace them, the hole deteriorates. Also, you have to seal the signs against water, and you don't want to risk damaging your new signs by removing them and then reinstalling them.
When you get around to the signs, consider using LED lighting behind them in place of the original incandescent lamps. Much brighter and will last probably forever.