T&T: 12 volt power to the PC?

[Thomas Averill]

As many of you do, I navigate using a laptop powered at 110v  ac by my 
boat's inverter which is then stepped down to a lower dc voltage used by the 
computer.  I have wondered if there is a power converter available that 
would step the boat's 12v power up to the 22v dc needed by the computer 
directly avoiding the necessity to turn on the house inverter. Not a big 
deal, but this would also be useful under some other circumstances such as 
with a car or other 12v source.

Anybody know??

Tom