A CodePen by Phil Sinatra. Insert @ Caret - Insert some html text or in this case an HTML entity at the cursor location in an input.

index.html

<div id="symbolsetter">
  <table>
    <tr>
      <td><input type="button" name="sym-copy" onclick="insertSymbol('copy')" value="&copy;" /></td>
    </tr>
    <tr>
      <td><input type="button" name="sym-reg" onclick="insertSymbol('reg')" value="&reg;" /></td>
    </tr>
    <tr>
      <td><input type="button" name="sym-trade" onclick="insertSymbol('trade')" value="&trade;" /></td>
    </tr>
  </table>	
</div>		
<hr />
<input type="text" size="50" name="heading_title" id="heading_title" value = "" placeholder="Title" />

script.js

// http://www.scottklarr.com/topic/425/how-to-insert-text-into-a-textarea-where-the-cursor-is/
function insertAtCaret(areaId,text) {
	var txtarea = document.getElementById(areaId);
	var scrollPos = txtarea.scrollTop;
	var strPos = 0;
	var br = ((txtarea.selectionStart || txtarea.selectionStart == '0') ? 
		"ff" : (document.selection ? "ie" : false ) );
	if (br == "ie") { 
		txtarea.focus();
		var range = document.selection.createRange();
		range.moveStart ('character', -txtarea.value.length);
		strPos = range.text.length;
	}
	else if (br == "ff") strPos = txtarea.selectionStart;
	
	var front = (txtarea.value).substring(0,strPos);  
	var back = (txtarea.value).substring(strPos,txtarea.value.length); 
	txtarea.value=front+text+back;
	strPos = strPos + text.length;
	if (br == "ie") { 
		txtarea.focus();
		var range = document.selection.createRange();
		range.moveStart ('character', -txtarea.value.length);
		range.moveStart ('character', strPos);
		range.moveEnd ('character', 0);
		range.select();
	}
	else if (br == "ff") {
		txtarea.selectionStart = strPos;
		txtarea.selectionEnd = strPos;
		txtarea.focus();
	}
	txtarea.scrollTop = scrollPos;
}

function insertSymbol (whichOne) {
	insertAtCaret(focusID, '&' + whichOne + ';')
}

// setup a listener for the focus of any input elements
var focusID; 

$(":input").focus(function () {
	 focusID = this.id;
});		

style.css

input[type="button"] {
  font-size: 1.5em;
}