how about a regular micro-atx power supply at the store that runs for liek 30 usd (I.E. emachines psu)
im pretty sure you mean something ot use in the car and the opus is sure something to use in the car and it is not only a mini-itx psu.
power stuff on the inverter works.
the is jeff mucha's mpeg box psu.
there is also a diy sproggy taht you can build
there is the stock dc-dc psu that comes with most mini-itx cases.
it all depends on your needs and then a power supply can be found for you