Fishmommy provided excellent resources for you to check out I will add that jimisnakes.com also has some locality and type info!

I would add that there are tons of boas that fall into the length limitations you have given--like, mostly all of them and especially the males of all of the types!!

I would stick with Bci's though since you're just getting into boas. Their husbandry needs are a bit more forgiving than those of Bcc's.