I just took delivery of mine last night ! They came from Car Builder Solutions in the UK. Their contact number is +44-(0)1580-891309. They cost me £18 for a pair and seem to be well finished and of good quality.
I'm glad they worked. Where abouts did you fit them on the window ? (ie centre, top rear etc). They certainly are easy to fit and seem to be relatively well made. I also think they look very nice on the car. Mine, although fitted, have not yet been tried as my car is very near to completion. Anyway, I'm glad to have helped. Thanks for letting me know.
Some cars used these items.
Most of these had them mounted in the middle of the window flap.
Some run without the flap.
Some run without the whole side window.
MkIV´s used slide window´s mounted on the side windows.