Get one larger than the wattage yours requires. An inverter that is too small will build up too much heat. My laptop shows the power supply at 75 watts. I tried an inverter rated to 75 watts and it got way too hot. I upgraded to a 150 watt inverter and have had no problems.
Home Depot sells a nice Vector 400Watt for your needs. I believe Scotty B has one, i have another model Vector and have been very happy with their product!
You are asking for the minimum, 150W should work. I've run my notebook from a cheapo 150W inverter for years. Notebook power supply shows 65W, I measured 37W when charging. The inverter does get rather warm. I now even run the 17in LCD from the same inverter...
I purchased mine at the local Staples. There are quite a few that look much the same. I look for a good metal body with cooling fins. I don't want a fan as it gets dusty and wears out.
I think I paid about $30 for the one I have. I have seen comparable inverters in the $50 range now.
I was wrong in my first post. I had a 75W that heated and bought this 150w that runs just fine.
Mine is a Fellowes 150W AC/DC Mobile power inverter.
In some discussions of inverters, I've seen claims that the inverter should have a 'modified sine wave'. I suspect, though, that that is norm these days. Still, it would worth checking the packaging for any description of its output.