Most of the bimacs that TONMO members have kept recently are captive-bred or tank-raised by fellow hobbyists. This is legal, since the animal taken from the wild isn't sold. A few companies have tried to do this for a profit; all have failed. Ultimately the market for these creatures is so small and uneven that I don't know if it is even possible to succeed at captive breeding for profit. Given this, I'm very skeptical of any claim by retailers or distributors (profit people) of having bimacs. Indeed it is always possible that a distributor ends up with a bimac that just happens to lay eggs, but I think this is unlikely for a few reasons: first, the vast majority of marine ornamentals are being collected in the South Pacific and shipped into California. Overall, temperate species found off California aren't in heavy demand and I suspect it's rare for animals of any type to be collected here for the hobby. California also isn't known to be the most permissive state to those whose intention it is to pluck from Nature. Baby octopuses are also very difficult to raise, they do best when given individual dens and fed live food like mysids ($$$). I doubt a distributor would bother, given the meager hopes for recouping any investment.
Given that, I know that Marine Depot sometimes has bimacs in, but in personal correspondence with them they're not afraid to give the impression that the animals are sickly, often missing arms. I don't know where they get them from, but I have not ordered from them so I cannot even confirm that they are, indeed bimacs. This brings me to another important point: it's very difficult--sometimes even for zoologists--to identify an octopus. Even when a hobbyist submits a photo of their beloved octo here on the forums they often don't get a good consensus. It is not realistic to expect distributors or retailers to know what type of octopus they're selling. The goal of these organizations is to move livestock and we can't expect them to have specialists in every niche organism. Most retail website images aren't of the octopus sold, rather just a generic picture taken off the internet (some of these people probably aren't aware there are multiple species of octopus!).
This is why I generally try to get cephs from fellow hobbyists. It is the only good way to get an animal whose identity, natural habitat and age you can be sure of. The problem with doing this is there isn't any guarantee of availability. This is not a hobby for the impatient, it will probably take months or years to find the species you're looking for.
Dan