An economical solution would be to simply use some black vinyl sticky overlay material. I believe people have indicated that PartsExpress sell this stuff. I believe you simply pull off the backing and then lay it on the control panel.
I bought my vinyl covering for my driving cabinet many moons ago from Happs ...... I got a great deal on the Black Pica Vinyl since it was on sale for something like 60% off.
Anyway, I believe enough people of these boards have used PartsExpress vinyl so you might want to seek them out and ask how the vinyl is holding up. Not sure you would even need to get plexiglass at all. Also, plexi can be expensive as well ..... depending on the size of your control panel.
BTW: For my standup cabinet I used plexiglass as a covering a used a a drill for the holes (ie: not router) and had no problems at all. The key to drilling in to plexi is to let the spinning drill bit spin enough to melt the plexi as it sinks into the plexi (with minor pressure applied). Typically, using a drill on wood, the person applies a lot of pressure to simply get the hole bored out, but with plexi minor pressure is key and just let the drill melt itself through. No problem at all. oh yeah, I used a jigsaw to round the coners of the plexi to match the rounded corners of my control panel.