Solution
1. Download an official updater (PRS-T1_Updater_1.0.05.11130)
2. Used 7-zip to extract its contents
3. In PRS-T1_Updater_1.0.05.11130.exe\eBookUpdater\scripts\u pdater.xml
find the following line:
"return updateVersion <= deviceVersion"
and change it to
"return updateVersion >= deviceVersion"
This way it will run the
firmware upgrade regardless of your current version -
except for some newer firmwares (e.g. 1.07), those check the version on the reader itself and deny it, if it's a newer one.