I still have a Nikon DK-17m on order at Adorama. There is an outside, outside chance they will find a few somewhere. eBay is selling them a gouge prices. Not finding many on eBay.
There was a time where used Nikon SB-800(s) sold for more than the new price just after the SB-800 was discontinued. Now the SB-800 can be purchased in decent condition at a reasonable price. This will hopefully happen to the DK-17m.
I can't use the DK-17m on my D850 while wearing glasses. I need to try half reader "granny glasses" to see if I can view directly above and then view the top LCD through the reading glasses. I hope I may be able to use the DK-17m with a D500 that I might buy with the proceeds from selling my old Ford F150. If I can use the DK-17m with the D500 that would offer a 1.2x viewfinder for focusing my legacy AI and AIS Nikkors.
Dave