My data plate had been painted over as well. I tried to get the paint off but wasn't able to do so without also removing the original paint. I ended up having to buy and stamp a reproduction plate. The screw you refer to is a combination hex/clutch head screw that I don't believe is being made any longer. I've searched and not found anywhere to buy any so don't lose them.

Original data plate.

Reproduction plate with the screw you mention.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.