I'm trying to find a source. I bought a whole bunch of them somewhere two years ago, but most disappeared. The few that bloomed look very nice, so I thought I would try again.
It has been many years, but I am sure I bought mine mail order from Dutch Gardens. I have not looked but Costco may have them by the box. Al
You might try Green Thumb/Green Arrow.
I thought I saw them at Lowes this year also.
So glad you asked, I'm planning to add them to the garden this fall. Have you searched on-line? If you can't find a local source, I found it at Bluestone Perennials, a very reputable on-line catalog.
I bought bulbs at Walter Andersen's in San Diego, but don't remember what time of year.
I like Brent & Becky's, a small but highly reputable mail order bulb supplier. I've ordered from them several times and always been pleased. For liatris, however, I think you'll have to wait a bit to order from them. The liatris are listed in their summer catalogue, and right now they're zeroed in on tulips and daffodils for the fall.
Here is a link that might be useful: Liatris from Brent & Becky
I'll look at Lowe's and Green Thumb/Arrow first. Wow, what a difference in prices! 8.95 at Bluestone for one bulb, and about 1.20 apiece at Brent and Becky's. Since I want a lot, I don't think I'll go with Bluestone.
The cheapo ones are as good as the expensive ones. Mine I've had since 2000 and they are still doing great. They like at least a little moisture year round, but to stay on the dry side. Neither totally dry nor very moist. Otherwise they either dry up or rot. Then let the plant growth really dry out before you cut it off. In a spot they are happy with, they are very easy.