I am looking for something like a USB adapter for video cards. It is a cable that on one end hooks into a USB port on a computer and on the other accepts any one of a variety of video cards. Essentially it's an "all-in-one" USB adapter for video cards.

I'm told that they are sold all over... does anyone know what it is called or where to find them?

I should clarify, by the way, that by "video card" I mean a memory card for a video camera, and that the goal is to read this video data onto a computer, from a variety of video card types, through a USB port. That way if you go to your friend's house and bring your computer, you can transfer the video data on his video camera to your computer, trusting that the adapter will have a slot for his kind of video card.