PSI makes it ($69.99) . I personally think your money would be better spent by buying either a collet chuck ($89.99 from PSI) or a scroll chuck ($179.99 for the barracuda 2) .
If you are making only pens then the collet chuck is much more useful then a dedicated blank holding chuck that really has no other use . You do have to turn your blanks round first to use the collet chuck but that only takes a few seconds and you can use it to hold mandrels and even make whole pens using just a collet chuck without the mandrel .
If you ever want to turn other things like bowls or boxes then a scroll chuck is the way to go , you can't do it with the drilling chuck but you can buy the blank jaws for the barracuda 2 if you ever feel the need (the pin jaws work very well for drilling blanks) . You can also use the step jaws to hold mandrels and other things like bottle stopper mandrels and closed end mandrels . The barracuda 2 comes with 4 jaw sets for any small turnings you might want to try in the future and a carry case to keep it all together , it's also a keyed chuck so you don't have to play games chucking things up with the Tommy bars (levers , it always seems like you need 3 hands to use them)