I am sad to know this. Apparently it is not as popular as people might think. At the time of writing [September 28, 2015], I have 6 pairs of black size C, and 2 pairs of natural size C. If you like this style, then stock up while you have the chance.
If there is a Energizers medium support colour that you would like to see in a waistless style, then get touch with me to customize them for you. I would take some regular reinforced waistless pantyhose, and then remove the legs, and then attach the Energizers legs of your choice.
Thank you for reading!