You can manually download the firmware updates using the links on Patrick Gaskin's
Kobo Firmware Downloads site for the links. Once you have the update for your 905C downloaded, connect your Kobo Touch to your computer and copy the contents of the .zip archive (the upgrade directory and the KoboRoot.tgz and manifest.md5sum files) to the .kobo directory on your Kobo. When you safely eject, the update should install and you should be able to connect to WiFi.