Right now, its not going to be very easy to locate any herb plants, as the growing season is now in full swing, and seedlings are mostly sold out everywhere. It may be prudent to start searching for herb seeds and start your own from seeds early next spring. Things like chives, basil, and dill are easy to grow from seeds, and can be planted directly in soil outdoors, or started in small pots and the transferred. Cilantro is also easy to grow, but to get a continual supply, you would start seeds about 2-3 weeks apart as once they bolt, they will not produce much in the way of useful leaves. Oregano and mint are also something that can remain outdoors all the time. Rosemary is also one that you still may find right now, but planting outdoors it could survive through winter in your area. I didn't plant a single dill seed outsied, and have it everywhere right now. Thats due to the fact that I let all the rest of the seed heads drop where they may. My dill is the mammouth type and most plants are nearly a foot tall already and have lots of dill weed leaves. I figured I would harvest most of the leaves once they strat to send out the flower/seed heads, and then let them come up where they want to next year too. I have some in my compost, 50 feet away from the rest, and even a few in my front lawn, and all these just came up where a seed landed. The nice thing about starting your own plants from seed, is you have a better selection to choose from, and don't have to settle for a puny plant at a nursery or garden shop, that may have been forced grown and would quickly die once you get it home.

You can try www.richters.com.
I bought all my seeds and plants there and found their prices to be reasonable and the quality of my plants was fantastic. They are in Ontario, Canada tho, I am not sure where you are from.

Hope that helps!

You might try The Tasteful Garden - tastefulgarden.com . They have the most beautiful plants I've ever received via mail and they're packed to perfection. Also, the people are super-nice and great to work with.