The original MadCatz TE panel is not plexiglass but some kind of printed laminate that’s been glued onto the metal panel.
You can still replace it with different printed artwork, or with a plexi panel of your choice. I have a few plexi panels available if interested, it just depends which particular style you were after.
Regarding the screws, you can find replacements very easily from places like eBay or local hardware store. The problem is that the original MadCatz screws seem unique in the size hex key they take, all the replacements you’ll find will fit perfectly but will have a smaller hex key requirement.