http://ereader-store.de/en/content/8-downloads
I did it for a T68. Works okay. Not sure about your device. Ask Booxtor if it will work. Note: The 4.4 upgrade is old and many people have had problems with it. Search Onyx 4.4 Kitkat. Personally it worked okay for me. Onyx will be releasing a 4.4 update this month, so you might be better to wait for that.