The supply of cheap genuine Bosch Fatpacks seems to have dried up and in Europe they never were available anyway.
What I can get now is a Titan-made clone of 2.2Ah for £52/€60/$84
http://www.a1-battery.co.uk/POWER_TOOLS_BATTERY/BOSCH/TBS043.htm
or a 3.0Ah for £102/€117/$165...