This was originally in my wife's 2015 VW Beetle that we sold several years ago when she stopped driving. The oil was only changed once while she had this car, so this valve is basically new.
The threads are M14-1.5 so it should work in a Miata too. One possible issue is that it might need a length adaptor to actually fit. Adaptors are $5-6 from Fumoto. The nice thing about this is the "L" fitting on the end that can swivel down when draining, the fitting can then be tightened down to stay up out of the way or even removed if clearance is an issue.
Only asking $15 shipped to the lower 48 for this.
IMG_1155 by Richard Velardo, on Flickr