I'm a little confused, when you say OEM plate are you referring to the one that comes with the car, or the heady duty VW "Underrun" ?
The posting by "Golfdave" is excellent, but it seems to only address gas MK7's, or am I missing something ?
He list the following part number : 3Q0 825 902 , but it appears to have been replaced by 3Q0825902-A
This tray is available here for about $280, but I can't find any description with it, and it shows fitment for 1.8TSI Alltrack, so not sure if it bolts up under a TDi car.
Ebay Germany has the following tray which also has the part number #Q0825902 listed as well as a lot of other numbers, but is a fraction of the price and doesn't look identical, so it's probably not heavy duty
https://www.ebay.com/itm/142494202310