Hunting for this piece, sharp eyes requested

[Dart]

Hi folks! I'm looking for a model piece and was hoping someone here might have some ideas on what it actually is. Here's the best image I could find of it:

I know this is made of 2 different kit parts and I already have the bottom, square bit (from a Tamiya Harley kit). It's the top bit that I can't find.

I'm thinking it's maybe some sort of oil pan from a model kit? It doesn't seem to have any texture on it that suggest a radiator of any sort, and it has that notch in one end (possibly both). It was one of those greeblies found on multiple costumes and parts from ROTJ (this image is from an Endor Commando backpack, but it was also used on the ROTJ Rebel pilot belt boxes and B-Wing chest box, as well as the Rebel Technician belt box).

Can't find anything like it so far, so I thought I'd consult with the vast brain wealth of the RPF. Any help would be greatly appreciated.

 

[Dart]

Bringing this one back from the dead! Found some better photos of what I'm looking for. Looks like some sorta radiator bit? Looking at the piece on the left. These are reference pics from the RS Props B-Wing Chest Box they're now offering. I realize that it might seem like contacting them would be faster, but I figured I'd take my chances here.

 

[Belugawrx]

Knowing the size of it might help in getting an answer

 

[Dart]

I actually think I found it. I believe it's from the Tamiya 1/20 Toyota Celica LB Turbo, Part E15.

But I'm not sure how big this piece is. The square piece that accompanies it is roughly an inch square.

*Edit* Found the item info on Scalemates and confirmed with the Tamiya distributor locally that they can order the sprue with this part from Japan! Wooo!