Dear Mr. Henderson
Here a link for a good quality spray paint I have used many times that has excellent adherence over plastic surfaces
Rust-Oleum 1911830 Vinyl Spray, 11 oz, White
https://a.co/d/7uetfKmAnd then ….. the numbers on the dials you can paint them with an acrylic pen. Let me look for one I have used before from the brand PENTEL.
Found this one with good reviews. Paints over plastic.
Posca Uni Pc-1Mr Black Colour Paint Marker Pens Ultra Fine 0.7Mm Calibre Tip Nib Writes On Any Surface Glass Metal Wood Plastic Fabric (Pack Of 3)
https://a.co/d/84O4fpmBest regards
L.Peterssen