Specifically, a SCSI cdrom audio cable worked although I can't recall if ATA and SCSI cdrom drives has identical connectors or not. Perhaps the SCSI one tended to be white rectangle without a retention mechanism while the ATA one was one was black thinner, and longer, with a retention mechanism.
3 of the 4 wires (RX, TX, and GND) would then be soldered to a DB-9 female plug.
You do gave to then splice that wire to a 9 serial. But thats not too hard and with some shrink tubing it'll look great.
[1] I think the connector is a fairly standard part.in the 90s, though, we were flooded with those cables so the tutorials just had us use those