The new Cobra and King Cobra are not Colt "D" frame models.
The old "D" frame was discontinued and replaced in 1995 with the then-new Colt "SF" frame.
This was Colt's new transfer bar safety-ignition model based on the original Mark III-King Cobra design.
Guns in this short lived series were the Colt SF-VI, DS-II, and Magnum Carry.
I haven't heard what designation Colt has given the new Cobra and King Cobra, but it would be the "SF" frame before it would be a "D" frame.
The actual frame and cylinder diameter of the "SF" frames and the new models are the same size as the old Colt "D" frame with some changes to beef up the frame in the top strap area.
The limiting feature of the new models is the re-shaped trigger guard that prevents it fitting holsters with covered trigger guards made for the older "D" or "SF" frames.
There are at least several makers now offering holsters specifically for the new models, but I can't remember who they were.
The info was posted on another forum.
I just did a little searching here's a few makers who list holsters for the New 2017 Cobra or the New King Cobra
https://www.galcogunleather.com/belt-holsters_8_4.html
https://www.simplyrugged.com/ecommerce/LEATHER GUN HOLSTERS.cfm?cat_id=669
HBE LeatherWorks Leather Holster Gun/Mold List
Ken Null says to contact him fore possible availability....
K.L. Null Holsters Home Page
https://www.kramerleather.com/collections/colt/products/iwb-2-holster
Best suggestion is to just call some of the better holster makers and ask if they offer models for the new Colt's.