Heidi, Susan and I love the "Paci" plugs (http://www.early2bed.com/mm5/merchant.mvc?Store_Code=ETB&Screen=PROD&Category_Code=sbt&Product_Code=PACI)
They are shaped like than a child's pacifier, and some in two sizes (there isn't much difference between the small and large). What we love about the design is the delightful "bulb" that fills us up, but yet they have a narrow neck that your sphincter can clench around. We also love the narrow round ring (instead of the traditional flanged base) this ring can nestle very comfortably between your butt-cheeks -- and thus not working to pop-out the plug as you bend-over to pluck items from low-lying grocery shelves! LOL!!
These are a lot like the ever-popular nJoy, but lighter (and cheaper!). Again, this is our favorite plug for long-term wear out in public.