With the help of another member, I managed to acquire a fully functional Superswitch Intruder Alarm, complete with box, wall mount, operating guide, stickers, and some other stuff.
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Superswitch Intruder Alarm.jpg [ 554.83 KiB | Viewed 5140 times ]
When I compared the Superswitch's grill to pictures of the grill on the Prop Store's Motion Tracker on display at SDCC 2013, they appeared to match, except that the Motion Tracker's grill looked like it might be very slightly thicker.
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SIA grill removed.jpg [ 909.55 KiB | Viewed 5140 times ]
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SIA grill close-up.jpg [ 1.1 MiB | Viewed 5140 times ]
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Prop Store MT grill.png [ 29.6 KiB | Viewed 5140 times ]
Also, since the section with the grill would have been removed from the Superswitch to make the Shoulder Lamp, it seems likely that's where the grill's from. So, if anyone wants an accurate Tracker grill, the diamonds measure 3 mm high, 2 mm wide, and the sides are 1.5 mm long.