Maybe I'm not calling them by the correct name. 1/32" thick rowmark with adhesive on the back. These are thin and small and stuck to the plaque. In the photo you can see some of the damaged letters on the top line of copy
Appliqué, I believe, is a type of sewing? I know a lot of people that refer to tactile lettering adhered to a sign as appliqué though, not sure why but it’s definitely a term I’ve heard before. Do you just want the lettering cut or are you trying to source complete ada signs?
You can order the 1/32" material from Hansen Supply or JDS, they both sell Rowmark brand. Gemini also sells it, under a house brand, I think it's called Duets?