Hi The seeds are avaiable as I have grown them before. I didnt find them that successful, wether it was my fault I'm not sure. So Im not the best one to advise :o)

Welcome to GoY too.

Eustoma are either tap rooted annuals, biennials or short lived perennials, all are frost tender.
Sow the seed at 55-61 deg f either in autumn or late winter, be very careful with them as they are prone to damping off, if you're going to grow them as annuals make sure you don't plant them out too early, say mid june, to ensure we don't get any late frost on them, plant in a neutral to alkaline soil that is well drained, but I think they would be better grown in containers in a greenhouse, they make nice cut flowers.
As to where you would get the seed, I would try google, hope this helps, Derek.