Daylilies and lilies are two different kinds of perennials...not related, BTW.
There are many daylily sources that you can mail order from. We just had a discussion about this very topic on a Yahoo gardening forum that I am a part of. One of the members asked the very same question you did. So, I have copied and pasted some of the answers to you. You will have to google the websites of the various places mentioned below in order to see what they have. Who knows...there may even be a summer sale going on in some of the sites right now....
I have gotten mine from Strong's Daylilies, have had nothing but great service from her and her plants are always large, with a bonus plant.
David Jewell (On Russell Gardens)
I have ordered from Red Lane Gardens in PEI, very happy with the quality & service.
Floral and Hardy is the place I have received daylilies from in the past. I have mixed reviews about the plant material from Betty. The root system and plants are small, but she does have a lot of selection. You may be able to find daylilies there with her that she is the only person selling as she has connections with some of the hybridizers and is their distributor in Canada. Karol Emmerich sells her daylilies thru Betty.
Montfort has a lot of daylilies also. Their plants are really nice! A number of years ago I took advantage of their $3 sale and picked up a whole selection of them.
I have ordered from Melanie Mason in New York. Huge plants!
Joe Hawkins specializes in spider daylilies. Great selection of spiders! Great plants too!
Nova Scotia Daylilies...huge root systems
Another place to check for where to order daylilies from is going onto the internet into the Far North Garden Web site and searching for 'daylily mail order'. There are quite a few threads about the various places to order from and you will get true and honest reviews about them.
If you have any questions about any of the mail order places mentioned above, please ask as I have close to 500 different daylilies here now and also am hybridizing my own too.
Enjoy the daylilies you do chose to order, as they are wonderful perennials to add to any garden!