Hi Averil,
I have this plant and grow it in a hanging pot with rocky substrate in a bright spot. A little calcium or limestone may help, too. Morning or late afternoon direct sun only. I would snag those seeds quickly! Try starting seeds in a pumice-type or very small gravel/sand mix with little to no soil. Keep your humidity high, like maybe in a humidity tent, but watch out for fungus. I have heard you can mist with weak chamomile tea for fungus problems. Good luck and take pics!

Hi crazyplantlady, many thanks for that! I think these plants are amazing. I'm off to order the seeds right now!! BIEEEEEEEEEEEEEE

http://www.kakteen-haage.de/en/plants/cacti/Hildewintera/

If all else fails, try this nursery. I got my original plant here. They don't ship to the US anymore, though. But they do to UK.

Right now, they have suspended shipping due to winter cold, but will resume in 2015.

Oh! And definitely use bottom heat when starting your seeds. =)