Body Ornamental Exhaust Ports

There are six pcs of separate ornamental chrome (with black painted insides), that go on the lower fender and doors. 3 per side and I am having no luck finding the replacement screw plug inserts (I call them), I don't know any dimensions except to say that the threaded insert is small. Anyone with knowledge of these plug inserts for the Dart GT, may be others, I'd appreciate the lead or even where I might find something that will work.

Thanks,