I have a full 100 foot spool of 3M 3302/20 multicolor ribbon cable on hand. That's the expensive part, $93 at Mouser new if you bought it there, or $45 for the solid gray 3365/20 ribbon cable.
If I was going to make a single cable myself I might pay full price for new brand name 3M connectors. I'm not sure what connectors DEC used, they are a slightly different style.
3421-7600 20-pin IDC
3448-3020 20-pin IDC strain relief (optional)
3490-2 20-pin IDC pull tab (optional)
(2x) 3473-7600 10-pin IDC
(2x) 3448-3010 10-pin IDC strain relief (optional)
(2x) 3490-1 10-pin IDC pull tab (optional)
That's $14 for all of those parts at Mouser, plus $8 for shipping if I didn't order anything else at the same time to spread the shipping cost over more parts. If I could find an original DEC cable for the M8189 KDF11-B 11/23+ console panel somewhere it's likely it would cost more than $22 with shipping.
If you give up trying to find an original DEC cable I would be willing to consider building one for the cost of the new connector parts and shipping. I have a 3M Scotchflex 3640 press and locator plate for IDC connectors, which makes it easy to press the connectors onto the ribbon cable. Before I got that I destroyed a few connectors trying to press them onto ribbon cable without the proper tools.