cloning USB sticks

so I'm a bit of a "belt and braces" sort of guy and like to carry spares wherever possible should the worst come to the worst and I loose my pen drive or it gets corrupted etc

can anyone recommend the best way to keep 2 sticks synced?

I carry a lot of tunes with me so my sticks are 64GB, whenever I update one I have to find a way to update the other. I don't want to put the second drive into Rekordbox because the data on the second drive might not be identical to the files on my primary stick (ie the one I tend to use live) as if I make adjustments to the grid for example or add/remove any cues via an XDJ at a club those amendments are written back to my RB library when I next connect to my RB libray which is good, but if I insert my backup stick into the PC, the amendments are then overwritten in RB and replaced with the original settings stored on the stick that hasn't been changed

Saving a copy of my primary stick to my PC's desktop then saving that to the second stick works, but is very slow

Think I might try something like SyncToy from Microsoft which should only add and amend changed files but if someone has a better solution please let me know?

George