I finally got to speak to a machinist who makes the part. It’s an additional (nominal) fee of about $17.45 not including shipping. So if anyone ever needs to know for future reference, here’s the data:
Tuff Nut T-Nuts Metric DIN Standard M8 (Bag of
Threaded Metric M8x1.25
Black Oxide finish.
Width: Neck – .378″/9.6mm, Flange – .571″/14.5mm
Height: Neck – .236″/6.0mm, Flange – .217″/5.5mm