the only real (and absolutely rare) outside chance you have of getting a new NAK is if you come across a store who has an unsold and boxed one left. There are 2 issues which should put you on the back-foot straightaway:
1) all NAKs are in very high demand...contrary to popular belief, cassettes are still in vogue to a niche audience and every audiophile still drools over the idea of having a NAK on his/her audiophile rack. In view of this, we guys have intensly searched every area possible and fished out every single NAK out there, for our racks...you're likely to find no more new ones left.
2) a new NAK which you might happen to find, boxed, is likely to be in a non-functional condition anyways as anything mechanical, which is boxed for so long, is not likely to work!!
The last NAK which came out was DR10 in the mid-1990s. Nakamichi has stopped producing cassette decks ever since. Honestly, Nakamichi was only good with its great line of cassette decks so, the moment the format became obselete, they had to wind up and sell out. Although the older NAKs may look very attractive and juicy (but very highly priced) in the pre-used market, it would make sense to go in for a more contemporary NAK, say the DR series..
my 2 cents!!