Sorry you're going through this. I mulled over the dilemma of buying an original grille or a repop for quite some time but in the end decided to go repop. The simple truth is, these 50 year old plastics are brittle no matter how they have been stored. Had I found one, I could have spent the money only to break tabs when installing on my car...let alone worrying about it arriving in one piece after shipping.
I would show them the value of a repop. This way you will get back the money you actually paid.
This is the one I bought. JEGS had them cheaper with a code. Hopefully you get acceptable resolution. Good luck!