You can look thru these:
http://www.knittingpatterncentral.co...c_clothing.php
The candy one at Knitty is good for a laugh:
http://knitty.com/ISSUEsummer04/PATT302calories.html
If you can't find a plus size, you could size one up by making the front triangle a bit larger, the back would be easy if it's just a narrow strip (just make it a little longer) and you could make the sides tie strings so size is easily adjustable.