Summary

Au$6 to buy from the dealer - each!
Made them myself instead.

Instructions

I printed in hi-res of 0.1mm and used 100% fill with only one shell layer.
I designed the circular head to be half round so that this twist lock faster can be printed lying down on the completely flat side. It needs to do this so that the printed strands run longitudinly for strength. ie: if printed vertically, it would almost certainly break when under pressure across one of the printed layers.
If neccessary, you can run a hacksaw blade through each of the flutes to clean it a bit better and give it better "grab".
I used this on the cover panel under the dashboard around the steering column and pedals of a BMW. I would think they can be used wherever a flat sided Xmas Tree fastener is used and easy access is required and simply rescaled for larger or small sizes.

Twist lock fastener