Hi JDS,
Good luck with your search. I too looked long and hard for a DT400. Found one on ebay early one morning and was happy to pay the 1K "Buy now" price. Last on I saw in Oz went for over 7k, restored. As an aside I saw a NOS high front mudguard which went for 300 hundred au. A bit rich for me, but in hindsight....
Here's some of mine.