I tried looking at the one currently on EBay I thought the might have been the back side of the lines that held the front engine covers on there is like a couple of pairs of those
I was wondering too.
I scanned through Karl Tate's Y-wing album on flickr. Its not a Master Replicas but should have the same greeblie somewhere.
I imagine the dark side is attached to the hull somewhere and the lighter side is the side to look for.
Didn't find it but it could have been staring me right in the face.