Seeing these vents are no longer available, I had to come up with a plan to repair them.

I did find some more information https://www.4crawler.com/4x4/CheapTricks/index.shtml#BpillarTrim

 

What I decided to do was cut up some square plant propergating pots to the size needed

 

I notched out a couple of vees so that the flaps could slide into the slides and butt up against the original moulding tags

 

Like so

 

Next I used industrial super glue along the top to secure the flaps

 

A view of the vent flaps from the outside

 

Vent the right way up so water and dust doesn't ingrese a well as letting pressure out of the cab as required