You can download the firmware from links on Patrick Gaskin's
Kobo Firmware Downloads. The last official firmware for the Mini was 3.19.5761-s but I have used 4.38.21908 on my Mini and it seems to work okay.
You may need to re-install the package since KFMon does not, AFAIK, survive a firmware update. Personally, the first thing I do after installing the One Click Packages is to uninstall KFMon since I use NickelMenu to directly launch KOReader and Plato.