Thanks to my other half making me tidy the computer room (not a small task) I found the broken switch and, more importantly, missing left arrow keycaps, from my NEC APC-H4100E keyboard!
And with a couple of adapters to convert AT to PS/2, and then PS/2 to USB ...
It works! On my Mac!
Although the long space bar is taking some getting used to.
This is the very keyboard that prompted me to join GH. I learned a lot of my programming skills on a keyboard like this many years ago.
Thanks to XMIT for the replacement switch