Yes, any of the racing supply houses will have built in fire-suppression
systems.  Required in racecars and simple to install.  On a vanagon, I would
do probably just the engine compartment, but you can run lines (they use
metal tubing like aluminum to supply spray nozzles) to anywhere.  The simple
ones have a mechanical  cable/pull wire to activate..You mount a T-handle
within reach and jerk on that, releasing the whole charge of whatever style
extinguisher you select...Makes a big mess..but usually stops the fire..Some
are electrically activated with a button and a solenoid..
  Also available and what I consider a 'must' is a quick-release bracket
that securely holds a portable extinguisher somewhere that the driver can
grab it while making an emergency exit from the vehicle.  You want the quick
release (but secure)  bracket because a loose fire bottle is not good if you
should have a high speed roll-over or something.  And you want to be able to
grab that extinguisher and take it out with you in a panic evacuation like
if you come across an other vehicle that has crashed or your old fuel line
starts a fire..
  I have mine alongside the passengers seat pedestal so you can access it
while still in your driver's seat harness, or the passenger can, or you can
reach it from the rear area also..
  Don Hanson