Check this thread out --> https://www.mobileread.com/forums/sho...d.php?t=142100
I think that an option that should work.. The firmware can be found at http://download.kobobooks.com/firmwa...rade-1.9.9.zip
I think the steps would be to ensure that Kobo Desktop was NOT active then attach the Kobo and place the files from the download as mentioned in that thread.
Again; I have NOT done this myself so have no idea on the accuracy of these instructions.