The design would also need to provide roughly the same capacity as a typical handgun and provide a means for the user to carry a reload and employ it in roughly the same amount of time that it takes to reload a typical handgun.
Four of these: http://www.taser.com/products/law/Pages/TASERXREP.aspx
One of these: http://www.safetyharborfirearms.com/KEG_12/keg_12.html
(Though personally, I'd go half-and-half: if two Taser rounds don't do the job, it's time to make big, ugly holes.)