Buy from other people. They will have colonies that have been established in a tank for a while. they will open faster, divide faster and look better.
Love the Reef has some REALLY nice colonies at pretty good prices. I would buy them all if I had enough space.
Jays might also have some, but I noticed they dont carry many zoas. Jays does ahve some nice big clams and all sorts of other corals.
Frank also has some nice zoas. He is always psoting in the "corals for sale" section. he has good prices and his zoas are healthy. I bought a few from him in the past.
There are other members that also have some nice colonies.
^ that post is full of zoas. I ahve been to his house and he has a nice set up. I bought a couple of corals from him that are doing good.
Disclaimer: No one asked me to post names or links. I just did it because I have done business with them in the past and I got corals/zoa from them that were healthy.
Frank and Dong always have nice stuff but as for online I would try out reefs2go.com. They have great reviews and have daily deals and past couple days they have had 10% off entire site and almost all zoanthids are $9.99 for 5 polyps, and for some pretty nice ones too. I am going to be placing an order with then within the next couple weeks. Got my clean up crew from them, all there free shipping packs go on sale every once and a while 25% off and added a bunch of like items turned out to be great deal.
i get my really nice zoas from the best website in the world. it is called bostonreefers.org lol. i can get a full colony for really cheap and i can see them in person before i buy them
Keep an eye on the tang, I have a 150 with a purple tang, granted it was 3" when I got it, it is now 8"+ and I feel he's running out of room, it'll be a shame to torture such a wonderful fish. My 3 tangs are my pride and joy