You can make 7/16" and 9/16" Mopar nuts out of generic castle nuts by grinding or filing off the unwanted parts. Avoid zinc plated generic nuts, since the Mopars are phosphated.

Mopar tri-castle nuts are fully forged, while generic castle nuts are typically sawn or machined on top. You'll need to make the sawn or machined parts look forged and re-phosphate your finished nuts or otherwise disguise the resulting bare metal portions.