the 320 is a 163 HP i6 available in Europe, Asia, and Africa. The 320 was not shipped to the US, South America, or Austraila (might be wrong on the last one, but I'm pretty sure the aussies don't have it either). Its nothing special. It includes the amenities of the 325 without paying for the 2.5L. The 320 is actually slower than the 318, hence why it was not sold in NA.
Pertaining to the question at hand, the grill slats would most likely have to be ordered from the dealer, if bavauto.com or bimmerparts.com do not carry it. a cheaper alternative is to go to a hardware store and buy mesh used to cover gutters on a roof. It is the same mesh sold for bumpers, only at costs about $2 instead of $20.
<span style='color:gray'><span style='font-family:Courier'>1995 e36 3 Series RIP
1999 e46 3 Series BURN IN HELL
2000 MR-S Roadster= Current</span></span>