Hiya Frank
There is no work-around...
SD Jukebox takes in MP3/WAV/WMA audio files or music on CDs and converts each song into a format that the KN7000 will recognise and play.
The SD Jukebox software is as you've discovered designed for use in PC's not in Apple Macs sadly - and was of course written as a bit of software at least 8 or 9 years ago...Technics stopped making keyboards 6 to 7 years ago, so there aren't any Mac inclusive updates to SD Jukebox.
If you've got a local friend with a PC who will let you load SD Jukebox and convert your MP3/WAV/WMA file plus download it to an SD Card...that's about the only way forward...
Good luck - Rog