You might try Dave's Garden and see what turns up. My own hosta source is a local grower so I haven't grown them from seed simply because I've no need to do so. I buy plants, not seeds, so I can't answer your question. The majority of my named hostas came from O'Brien Hosta in Granby, CT.

http://www.obrienhosta.com/

They have an excellent reputation; John O'Brien is totally cool and has selected the best plant he has for me whenever I've visited.

Sometimes, especially later in the season you can find them in the Hosta Library auctions.

Were you able to find any seed this year, and how is the growing coming along (if you're growing seedlings indoors and/or they haven't gone dormant for the year)? Would love to see pics :)

By the way, there are lots of hosta seeds listed on eBay now (I just checked again).