You've gotten some good replies here. I've always found it interesting that this boat is not more widely available or that what is available is not better cast/designed/detailed. USN 571 deserves better.
There are options in all of the typical naval scales:
1:700 - Pit Road makes a plastic kit in this scale - just a few parts (two hull pieces, sail, props, vertical fin, and periscopes) Hobby Link Japan has had these kits in stock recently. There's at least one other Japanese company that made/makes the Nautilus in 1:600 - 1:700 scale range, but I suspect the PR kit is the more accurate. PR kit is full hull, many subs in 1:700 scale come waterline version only.
1:350 - Pit Road/Combat Subs kit, referenced above. I don't own this kit, but every other resin sub I have in the PR/CS series has been flawlessly cast.
1:192 is another "common" scale for display submarines. I don't collect or build in that scale, but if you want to build up a collection in a consistent scale, 1:192 offers some choices.
1:350 scale probably offers the greatest range for accurate detailing, etc. 1:700 probably offers the most varied range across technological eras and navies.
Lindberg and Revell made and continue to reissue their box-sale kits of this submarine. Aurora also made a kit. Re-pops and originals are frequently available on Ebay, but not worth buying but for nostalgia and the box art of the orginal releases. No consistency with other sub models out there, and of limited accuracy re hull shape and dimensions.
Scientific Model Airplane Co of NJ made a Nautilus kit from wood in the 1960s, but my recollection is that it was not scaled well enough to serve as a base for scratchbuilding.
Group Build (Shiver Me Timbers):
1:200 Trumpeter Arizona, 0% complete
1:700 3 Flight Deck Akagi, 10% complete