Are you looking for an OEM backup camera or an aftermarket one?
As far as OEM goes for the 2013's I can't really help you....
For aftermarket there are tons of options though. I just added a Audiovox camera to my 2012 and hooked it up to my Kenwood head unit. Since you have the stock radio that won't be an option but I know there are tons of companies out there that make aftermarket set ups that either use externally mounted monitors (almost like a little GPS screen that you can suction cup somewhere) or ones that are integrated into the rear view mirror. Typically high end audio shops will carry that kind of stuff as well. I would hit up some of your local shops and see what they've got.
Here's my thread about my backup camera install: http://www.ramforumz.com/showthread.php?t=145890
As you'll see you don't need a new tailgate handle (at least you don't on a 2012). You can just drill out the location of the OEM camera on your existing handle.