Sorry to dredge this up as my first post, but I came across this thread...I don't even remember how. I've never even seen the movie. I searched and searched and realized this is still unresolved.
I can tell you that the part you are looking for is not a single part. It's 3-4 parts. The grill seems to have been narrowed. There are cut and glue marks on both examples shown. The mounting tabs are fabricated, not part of any of the parts. I have a hunch that the grill comes from an appliance or radio. I swear I've seen that exact profile before.
Here's what I think might be the construct of the parts.
I think the Grill was part of the case of something. The far right opening is narrower than the others. It has a seam line, joining up to the endcap. The endcap definitely belongs to the grill. It has the exact same profiles. The shape I show in the picture is just a guess as to what it originally looked like. I'm assuming they chopped it down because it was too wide. Since there is a seam at that spot, there must've been more material or some other construct on the original piece that wouldn't look good. Hence, the wide spot.
The box on top of the round part at left is almost certainly part of it. The joint where the two meet is perfectly uniform, seen here.
I really think that the little cap over the middle hole is a silver thumb tack.
Grill:
Possibly from an intercom? Power Supply? Radio? I could almost bet it's something that used a large transformer. That, or it contained a rheostat.
edit: oh, and the ring around the hole? Whatever was glued on there got knocked off of both of them by the Mic boom.