You would have to do some looking, but there are printers that use 12 VDC and can be powered directly with 12 VDC. If you're unable--or unwilling to do that, then you may want to look at a small inverter. Inverters that would deliver 80 to 100 watts at 120 VAC are available for $10 to $20 bucks. Those would be ideal for running a small printer. Of course, you would be reconverting twice, but if you can't find what you need, that may be the easiest way of doing what you want to.