I know Gurney's and Burgess both sell them through their catalog but I'm not sure when they ship them out. You probably won't be able to get them in until Fall at the earliest or possibly spring.
I did get a veggie seed mix from Burgess and they have done great and a great value. They had a special for a veggie variety that had 12 of your basic garden veggies: corn, pickle cukes, large tomatoes, beans, lettuce, radishes etc. for only about $5 (give or take a few cents)
They have several varrieties of asparagus.