No I'm afraid there isn't, the best you can do is to add
" javascript:void((function(){var e=document.createElement('script');e.setAttribute('type','text/javascript');e.setAttribute('charset','UTF-8');e.setAttribute('src','http://assets.pinterest.com/js/pinmarklet.js?r='+Math.random()*99999999);document.body.appendChild(e)})()); " (no parenthesis)
as a favorite and name it Pin It.
Clicking the "Pin It" favorite while on a site will open an overlay so you can add it to a new tab where you can place the image to a board. Unfortunately it works from the upper fav bar or fav button next to the address bar and NOT from the side bar.