I know that Murray McMurray sells chickens that are on the watch list, can you go to their website and see if you can find the breed you are interested in? Goggle it? What type of chicken? Good luck!
Are you talking about something that is on the government's official endangered species list like the Prairie Chicken or are you talking about chickens like those on the ALBC's website as being "endangered"?
It is illegal to have wildlife, like the Prairie Chicken, but the chicken breeds such as those listed by the ALBC as being threatened/critical are ok to have. In fact, they WANT people to have those types of chickens and try to prevent them from becoming extinct.
I am expecting chicks from a threatened breed soon myself.
LOL - I understand. I just figured I'd throw it out there. My husband is a vet and on occasion sees things like that - you can just imagine the the illegal animals that people collect, sometimes purposely, more often just not knowing that they aren't supposed to have them.
The ALBC has the Redcap and the Russian Orloff on the critical list - which is REALLY not good and those guys need people to help with breeding to get their numbers back to higher levels. Here's the link to the list : http://www.albc-usa.org/cpl/wtchlist.html#chickens