I managed to find some Giant Milkweed (not sure of the cultivar) seeds on the internet and ordered some. 10 seeds. Only 1 so far has sprouted, but I'm happy to even have one growing! I think the Monarchs will be happy too when it is placed outside. I got the seeds from Georgiavines.com
I also bought some Asclepias fruiticosus seeds which I've never grown before. All germinated!