A Floppy cable for the Dragon can be easily made from a standard PC floppy cable.
The important bit is to remove the twist in the cable, and then only twist lines 10 and 12 as in the following diagram:
You don't need to use all connectors shown, just the ones you need.
The drive numbering assumes PC floppy drives are being used, which have the Drive Select signal fixed at DS1. If you intend to use original Dragon floppy drives, adjust them to DS1 by changing the right jumpers on the drives.
An example of a cable assembled using this diagram can be found here.