Obviously, you've gotten a lot of suggestions! There a many boas that stay relatively small so you have a lot of choices. Pick whichever one speaks to you. Boas are fantastic pets as you've probably already found so you can't go wrong no matter what.

I personally also suggest a Dumerils boa, but a male BCI will generally stay under 7 feet and are a bit lighter bodied than the Dums. And you have an infinite variety of morphs to choose from! Enjoy picking one out!