I'm skeptical you could even find a dwarf. If there was an octo that was small and readily available then everyone would have one.
Most distributors and retailers aren't very knowledgeable about cephs. In one case (O. bimaculoides vs. O. bimaculatus) you need a biology lab to differentiate the two! If you talk to your LFS, the most they'll probably be able to do is tell you they have "brown octopus" or "bali octopus" available on their stock lists and offer to order one of those. They won't be able to tell you what it is, where its from, or how old it is because they don't know--someone netted it while spraying cyanide in holes and sent it to the USA with the clownfish! If you find a fish shop willing to sell you a dwarf octo do you really think they know how to identify it?
The biggest exceptions to this are the octos that most TONMO'ers regularly keep. Bimacs and briareus can both be caught by divers here in the US. You can order one of these from east or west-coast fish shops and have a reasonable expectation of what you're getting. If you're serious about wanting an octo, you should really consider setting up a good sized tank for one of these species because you'll have a much better experience.
thanks dan. Gulf Coast Marine labatory says they have joubins for sale. I would assume they arte truely dwarves as they are a labatory. Heres the LINK.
I asked if they could get me a juveile species and they said yes but for $80 instead of the normal $29 for one. Forgot to ask if they are 100% sure they are joubinis though.
Dont look at LFS's specifically even though they are helpful believe me. But like at my shop we did get an octopus shipped to us as "Caribbean- sm"... um ok that doesn't help much...
Find collectors. You can do that online. If you want a Caribbean species, find a collector in that area. It'll be hard and worth a pretty penny for them to do a special order. and be sure to check them out to make sure they know their stuff. Most of the guys I know are very down and knowlegable with their livestock who want to see the animals do well. It can be a hassle, but it will definately help to narrow down finding the correct speicies.