I buy alot of zoanthids online from Coral Fanatics dot com.
I have had very good luck through them.
With any zoanthids you purchase, you should do some kind of dip on them. Just to help get rid of pests. I would especially dip zoas I bought on line. No disrespect to anyone, but I even dip stuff I know came from a healthy tank, just my preference.
I have never purchased from the place you listed, but I am sure someone on here will give some info on them.
Good luck.