Some of the LFSs do sell briareus online. Someone listed a couple of them within the last two months on these forums.
It's a tropical octopus (the Caribbean Reef Octopus) so it requires warmer temperatures than a bimac - maybe mid seventies.
You'd still need a minimum 50 gallon tank - this octopus has very long arms.
Otherwise, requirements are much the same as listed on the Bimac Care Sheet.
Nancy