-- Last Updated: Jun-11-12 8:19 PM EST --
http://www.oceankayak.com/kayaks/tandem_kayaks/
Despite being tandem sit-on-tops they are capable of being paddled by a single paddler and have a capacity way over your weight.
The only problem I can foresee is the sitting positions. If you have your weight too forward or aft it will make for a very awkward and unpleasant paddling experience. Definitely a 'try before you buy'.
Edit: sorry to repeat advice already given, the above post "Go Bigger" wasn't there when I composed my message.