So following up to myself. Of course I could have asked myself how likely it is that a PC store would have a 44 pin 2.5" IDE cable. They don't generally have them - though suggestions for places that do are most welcome. The alternative seems to be to recrimp this cable, but then I need to find somewhere that sells a crimping tool, connectors, and so forth.

Probably, it's best to just not be inpatient and wait for the Eutronix one I just ordered the "extended" cable since I'm hoping that is slightly longer between the host board header and the first drive...but I asked them to send the OEM one if that's not the case - I don't plan on using two drives, so having 2" of extra cable between the connectors is fairly useless.

Indeed it's not in the MX5 yet, but now that I can upgrade it (having setup a virt instance to run the Rio tools), and that it actually works (aside from the disk cable), I feel that next month will be finally the time to do it

Jon.