Coincidentally I posted this to another forum this morning. This is a frustrating part to find for sure. At least it may pan out to be another lead to rule out.
I think it has many similarities to a National Panasonic Cougar radio line from the 1970's. If an actual radio wasn't used perhaps one could have been a base for a mold? I haven't found an exact match yet though.
I have a scale model of the No.7 or RF-877 that my wife recently picked up for me in Japan. She just thought it looked cool, it immediately reminded me of the Sandtrooper radio box.