The Advanced Elements AirFusion is about the narrowest inflatable I have seen. 24" wide or so.
There is a review of it in the Spring 2011 issue of California Kayaker Magazine (readable for free at http://www.calkayakermag.com/magazine.html).
While you are there, you may want to read the article in Summer 2012 on Kayaking and Small Living Places to see the various options, and pros and cons of each.
Pull-Up Strap Handle Kit
Kayak Motor Kit
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