I agree completely with the comment below.  Many people will build a complex electrical system to avoid the vacuum pump, but having a pure mechanical system as a backup is protection against the time that all the electrics go away.  I designed a system that would power a vacuum instrument without the use of a vacuum pump in a turbocharged aircraft.  I ended up going naturally aspirated (both me and my engine :-), so I didn't implement the idea on mine.  It is essentially a pressure regulator that picks from the higher of compressor discharge and atmospheric pressure for the high side and the lower of atmospheric and intake manifold pressure for the low side, always maintaining a constant differential pressure across the instruments.  Therefore, the system will be powered all the time the engine is running regardless of power condition.  I patented the idea, but then got no interest in the product at the time so I dropped it.  Any interest out there now?