Bosch has a new battery system - power4all. This means their batteries are now interchangeable. Unfortunately, it's got an unique identifier and thermistor it requires which means it won't work with Makita batteries out of the box. The Bosch power4all vacuum cleaner however, is a nice bit of kit - albeit a bit expensive - as are the batteries.
By adding a small 1.5k resistor to ground from the second pin, and adding a 10k resistor to ground to the thermistor pin, you can run it off of any 20v battery power source, as follows:
(Excuse my soldering - this was done using a TS80P which simply did not have the power to solder these large connectors. )
You can also do this internally, and fit a makita battery holder like this, converting your bosch vacuum to cheap and plentiful Makita batteries like so: