Thanks for the reply and link.
You are right, I could use all sorts of 0.1" and 0.05" pitch conventional cables. But I would have to change a lot of connectors. Most 0.1" connectors have two rows spaced 0.1". These are spaced 0.2" on the board. So quite a bit of mangling would be required, There would be 20 sockets (10 cables) on each HP85 to change to allow for different cabling standards. And then, if anything fails, I have to mangle yet another "donor" unit from another HP85 to fit it, instead of it being a straight swap. I am not that keen to give myself a downstream headache like that yet.
I still feel that, as 2.54mm Flat Flexible Cable sections are very much still available (but in quantity) that I should try that route for now. If I can get a bunch of surplus FCC cables - 20 way, 0.1" pitch and some inches long - or a small reel of the cable itself, I can solve the issue a lot more easily and appropriately. I mean the correct flat-metal conductor type, not stranded, by the way. I can also help out my fellow HP85 enthusiasts with replacement cables.
So thanks, but still looking I am afraid .....