Is this what you're talking about? Not the best pic, it was taken at night during a rainstorm. Disregard the tag, that wasn't from them.

If it is what you're talking about, I've grown them a couple times, but from my experience, I'm not sure how they would do as a hanging basket plant. I've grown them both in ground and as a container plants and they seem to have a more upright growing manner, reaching about 2ft tall, not mounding like the more common impatien, more like their wild relative the jewelweed. Granted I never tried pinching them back, just kind of let them do their own thing.

But as far as growning them, they are fairly easy, like moist, rich soil, semi to most shade, and bloom all summer. They do make a nice accent plant.

Sorry, can't help you as far as to where to get them. I have a couple Mom and Pop nurseries near me that specialize in unusual plants and they are kind of a hit and miss thing as to if I can find them, got lucky this year. I'm going to see about taking cuttings or collecting seeds this fall.