Offline-Edit with Audio files

I have all my source footage on an external SSD and edit on the go using proxies on the local drive of my MBP. It works fine but I cannot transcode audio files (which makes sense) - so they are offline as soon as I disconnect the drive. Is there a way to automatically copy those files to my proxies folder? Otherwise I have to copy manually and relink - but then when I clear my MacBook and open my project later on - everything is offline again..