The old chemist's axiom is "Like dissolves like." Which means that in general inorganic chemicals will not dissolve in organic solvents and vice versa. There are some exceptions to this rule but it generally holds true. Your best bet would be a dispersion of colloidal silver iodide in the plastic. This is what is done in photo-gray eyeglasses.
I was thinking nanopowders also , they mix with acrylic very well , I think they made extreme high refractive index plastics with tio2 powders but when it goes thick , it cracks , thats why these mixes stays as coatings , may be I can coat glass with it. By rotation.
Where can I learn how much powder pmma mix makes highly wide range of tones or does it stay in 3-4 tones. Is there anyone knows the sensivity ?