Like naj's 113, mine too is devoid of these parts for the same reason. I can easily make that part. Could someone (66andBlue or others) take their calipers and give us some measurements?
e.g: Thickness of stock, length, width, height, distance between mounting holes, dimensions of 4mm square captive nut, etc.
Blueprint drawings would be nice but not necessary.
Thanks in advance - Mait