A friend of mine does a protective plate for the OBD connector.
This is a made to order, fit to design yellow plate with screws. See picture attached. It is a customised fit to OBD cover plate shape hardened material plate specifically designed for this purpose.
You may (for additional security) use tamper proof screws as well.
Not a 100% proof solution; but it does prevent anyone getting easy access to the OBD portů.
It is purposefully done in Striking Yellow to give it max visibility; as one of the key points of avoiding theft is to show the potential thief that you have some sort of protection mechanism - and thereby it is not worth his while to attempt theft on your car.
If you are interested in buying this
; I can forward your request to my friend. PM me for details...