The snake in that link is a BCI. BCC have a very red tail and generally get larger than BCI but take like twice the time.
You are right, Colombians are BCI. Guyana are BCC.
You will not find a "small" BCC. If you are looking something small like a dwarf boa, they are BCI. With that said, if properly fed, BCI and BCC are not going to grow fast. Boas grow very slow. My 6.5' BCI girl is almost 4 years old and honestly, I don't even notice how big she really is as I see her every day. Other people are like "omg that is a huge snake". She is pretty heavy as she is a female so she is thick. My sunglow BCI girl is about 5' and she going to be 3 years old in May. It will be very rare to find a BCI that hits 10'+. A BCC can do it but it will take years for it do that. I would guess somewhere in the range of 6-7 years if even that soon.
And generally boas are very mellow. Heck, Rosey my big girl has never hissed or struck anyone. About the only thing she does when someone else holds her is go into focus mode where she will do anything to get back onto me. Once she is back on me, she will look at whoever was holding her and inspect them lol. She's like my big puppy. Just have to interact with them a lot. When Rosey was a baby, I used to take her out all the time and hold her. I completely trust her. I can reach in and grab her face or tail or whatever and the worst she will do is turn away from me lol. Funny part is she was my pet store mutt, my first boa but she is my most special girl.
Also if anyone tries to sell you a morph BCC, be careful. Generally BCI are the morphs. People will breed in BCC blood to change the color of the BCI morph but to most BCC purists, that is sacrilege. If you are looking for a BCC, check out Star Shaffer on Facebook or you can ask Legacy Reptiles or Cutting Edge Herp. They deal in pure locality BCC and BCI.
Also what are you looking for as far as a BCI go? Are you looking for a morph? If it is not stated in the sale that it is BCC or Guyana or Suriname or Peruvian or Brazilian, then best bet is its BCI as BCC are more expensive except for some BCI morphs.
Also Boakid aka Richard Ceniceros has some really nice for sale. Maybe send him a message asking about any normal or cheaper hets.
Also I've seen Hec 1 aka hector Gonzalez selling lots of stuff too for a long time. Maybe check him out.
ShadowAceD aka Diem Marie sells very good stuff. I would trust her 100% for her stuff. I would bet she has a het that would fit you. She actually is starting to breed Scoria Boas too as well as Ryan something who I cant even remember his name lol.