One can be built I think... you need to get hold of a 50pin highdensity connector and cable. Then take an old dead SCSI unit and desolder the 50pin male connector (make sure it's one with plastic around to fixate the legs when it's off).
Then it's just a matter of clamping on the highdensity connector onto the cable and then soldering whire 1 from the cable to leg 1 on the bigger 50pin male connector and 2 to 2 and so on trough all 50. Keep this cable as short as possible so you can have longer SCSI cables attached to this.
