4x2 is standard. Nearly any brand as long as you can afford it. Boaphile is a popular brand (all one piece of molded PVC) but they are more expensive than say, Animal Plastics.

For me, the difference in quality is negligable and the cost of Animal Plastics is nearly half shipped versua Boaphile's same size cage.

Animal Plastics would be their T8 model cage.

I cant help ya with breeders. Big Apple Herp, LLLReptiles are two well known boa breeders.