There are two types of Blackbellies. Barbados and American. American are MUCH more common and to be likely what you will find if you happen to run across any in your area. REAL true Barbados are extremely rare, there are only about 1400 registered individuals in the United States. A starter flock of them can cost from about $1400 and upwards, depending on how far away a breeder is and shipping costs. To find a breeder in your area you would check here; http://www.consortium.blackbellysheep.info/ Maybe join if you are serious about getting into the breed. I have talked to a couple of the members and they are SUPER helpful and nice about trying to get additional flocks established.
If you just want regular American Blackbelly sheep, you can find them on Craigslist usually.
Hi there! I just purchased a small flock of (true) Barbados Blackbelly Sheep. WhiteMountain is right, there are 2 types. The American variety is a composite breed, with males having horns.