Is there any aftermarket 70-72 Dart grilles? Or anything else that would work?

The original grilles aren't that difficult to restore. Time consuming and tedious to restore, yes, but if you get one that's not completely thrashed they can be refinished. Anything cracked or broken can be epoxied, then the paint sanded down and repainted. I refinished the one for my Duster/ Demon tribute car, and even painted it a little bit darker metallic to fit my tastes. Maybe I've just been lucky, but I've purchased a few 70/71 grilles for $150-$250 that were in more than decent enough condition to go back in after a little refinishing. I don't know of any aftermarket grilles for the 70-72 Dart's, but if there were I would imagine that they wouldn't be under a few hundred bucks. The E-body grilles that are re-popped are like $1k.