You would need to use one of the links supplied in the
Direct Links to Kobo Touch Firmware thread, then, open the Kobo-Update.zip, expand the KoboRoot.tgz within it (that in turn will expand KoboRoot.tar), then navigate to the /usr/local/TrollTech/QTEmbedded-4.6.2-arm/lib/fonts directory (phew that was a mouthfull) and copy the fonts!