to TONMO, Sean!
I've moved this to the "exotics" forum with a temporary redirect, I apologize for any confusion.
As far as I know, there is no reliable source for Nautilus for the hobbyist, although they do show up occasionally in local fish stores.
Many of us consider the low availability to be a good thing: it's not really clear what the survivability of the species in the wild is (it hasn't really been studied) but there is a great deal of evidence that they are under a lot of collection pressure by people who want to sell their shells.
Our usual advice is that they don't make good pets anyway, so we don't really recommend them. Since you seem to have a handle on the needs (chiller, etc) I assume you know fairly well what to expect, and I don't mean to say that they are completely inappropriate for everyone (in fact, gjbarord and marinebio_guy wrote an article in TFH about keeping them, which you should probably take a look at if you haven't already.) We feel pretty strongly that many people who show interest aren't willing to provide a healthy environment for them, and, more importantly, that the collectors that send them to local fish stores make no effort to send them to people who are prepared to take care of them... and we also get questions here from people who want them as their "novelty fish of the week," and we're very concerned that increases in that trend could lead to them being overcollected and dying in fish stores or the hands of unprepared hobbyists (although whether that would be significant compared to the obscene number collected and killed for their shells to be sold as objets d'art is probably a fair question.)
Read here for some information on this:
The Perils of the Pearly Nautilus - The Cephalopod Page
Since you seem to know all this, I think it's a fair to try to answer your question in light of all that. If someone is wanting to keep Nautilus, and is responsible enough to provide a safe environment, what is the most reasonable way to obtain one? I know that many sources (e.g. the NRCC) don't provide animals to anyone except researchers and public aquariums. I'm pretty sure it's a bad idea to order from regular hobby suppliers and the like, because we've seen from experience that if collectors perceive a demand, they'll aggressively collect animals and ship them to local fish stores, where they'll either die because they don't know or have the resources to provide for them, or be sold to rich idiots as an expensive exotic, where they'll meet the same fate. (In case it seems harsh, I think the fact that you're describing responsibly setting up an appropriate tank in advance makes you quite different, so I don't mean to lump you in to the same category.) There are some collectors who are aware of the concerns, and collect for academic institutions. I know some have a blanket policy of never collecting for anything other than research or education, but maybe there are some who are willing to sell to qualified and prepared hobbyists in order to avoid the horrors of the mainstream ornamental fish pipeline. If there are, I imagine some of our members who have kept them professionally might be able to help you find a source, but I don't know for sure.
This raises an interesting moral question, since clearly at least Adam and Greg B think it's OK for advanced and prepared home aquarists to keep
Nautilus as a pet, but I don't remember their article suggesting how to obtain one without contributing to many of its cousins being killed by indiscriminate collectors shipping to unprepared LFSes. I'm not sure how Robyn, who works with them professionally, feels about obtaining them by asking, as you have, how to get one when properly prepared: I know she discouraged someone from trying to quickly set up a tank to rescue one from an LFS, since she felt that buying it from the LFS would encourage them to order more. Certainly, Dr. Monks, in his article above, would say that the only answer is "don't."
I try to be a realist, and think that people who are passionate enough about trying to meet their needs shouldn't be slapped down, and the primary villains are the shell collectors... this forum is something of a compromise there: to read the "Exotics and Rare Species" you have to register, so it's not indexed in google, and at least provides some requirement that only people serious about caring for these animals participate, so please keep discussion of
Nautilus in the home aquarium here.
In addition to Robyn, Adam, and Greg, I believe Cuttlegirl has worked with
Nautilus at the Waikiki Aquarium, so I'd encourage you to ask any or all of them for advice on the details of your setup.