Where can I find/make paintable opaque green domes?
If you're going to paint them anyway, especially opaque, I suggest spray-painting the semi-spheres. That way, you can get the exact green hue you want them to have, you can control whether you like it glossy or matte, and - dependent on your skills - can have them look really smooth.


I suggest sanding these transparent domes a little first, with very fine sandpaper (≥ ~300);
applying a layer (or two) of the spray-paint. To prevent the light plastic domes from flying away when paint-brushing, tape them on something heavy (like a wooden plank) with double-sided tape;
gluing the custom images onto the surface (depending on the paper by letting them soak in the glue, so they will follow the curved shape of the domes closely); 
and finishing it off by applying a layer of transparent (glossy or matte) varnish.