They seem to be available all over now. I got one last year from radio shack for the wife's tahoe so the kid could watch movies if we took a trip. Got a 600watt unit and it runs a 12" tv vcr combo and a nintendo with no issues. I think the 300 watt may be too small for stuff like that.
Check the label on your laptop to see what the power consumption is and get one rated a bit above that at least.
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