extending the FJ270s batt?

Question:
extending the FJ270s batt?
Is it possible to buy a higher FJ270 batt capacity?
http://www.circuitcity.com/ssm/Sony-...oductDetail.do
I like the notebook above but i think it states 1.5-3 hours but I want more than 4hours.
any options aside from paying $299 for a "sony" battery?
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